This set of Object Oriented Programming (OOPs) using C++ Multiple Choice Questions & Answers (MCQs) focuses on “Multiple Inheritance”.
1. Multiple inheritance is ____________________
a) When a class is derived from another class
b) When a class is derived from two or more classes
c) When a class is derived from other two derived classes
d) When a class is derived from exactly one class
View Answer
Explanation: The multiple inheritance is used when a class is being derived using two base classes or more. This way a single class can have features of more than one classes inherited into a single unit. This lets us combine two class members into a single class.
2. Which problem arises due to multiple inheritance, if hierarchical inheritance is used previously for its base classes?
a) Diamond
b) Circle
c) Triangle
d) Loop
View Answer
Explanation: The diamond problem arises when multiple inheritance is used. This problem arises because the same name member functions get derived into a single class. Which in turn creates ambiguity in calling those methods.
3. How many classes should a program contain to implement the multiple inheritance?
a) Only 1
b) At least 1
c) At least 3
d) Exactly 3
View Answer
Explanation: For the implementation of multiple inheritance, there must be at least 3 classes in a program. At least 2 base classes and one class to inherit those two classes. If lesser, it becomes single level inheritance.
4. Which programming language restricts the use of multiple inheritance?
a) C++
b) PHP
c) SmallTalk
d) Java
View Answer
Explanation: Java doesn’t allow use of multiple inheritance with classes. But this can be done by using the interfaces. This is more secure and unambiguous way to implement multiple inheritance.
5. Is it possible to have all the abstract classes as base classes of a derived class from those?
a) Yes, always
b) Yes, only if derived class implements all the methods
c) No, because abstract classes doesn’t have constructors
d) No, never
View Answer
Explanation: The condition for abstract class applies same here too. All the undefined functions must be defined. Hence all the base classes can be abstract but derived class must implement all those undefined functions.
6. If class A inherits class B and class C as “class A: public class B, public class C {// class body ;}; ”, which class constructor will be called first?
a) Class A
b) Class B
c) Class C
d) All together
View Answer
Explanation: The constructors of parent class will be called first. In that, the constructor of the classes will be called in the same sequence as that mentioned in class definition inheritance. Since class B is mentioned first for inheritance, its constructor will be called first.
7. Why does diamond problem arise due to multiple inheritance?
a) Methods with same name creates ambiguity and conflict
b) Methods inherited from the superclass may conflict
c) Derived class gets overloaded with more than two class methods
d) Derived class can’t distinguish the owner class of any derived method
View Answer
Explanation: All the derived classes can distinguish the base class members, but if a method is being inherited to the base classes from another class which again gets inherited into same class (diamond shape), that may create conflict in using the function from two available.
8. How many base classes can a derived class have which is implementing multiple inheritance?
a) Only 2
b) At least 2
c) At most 2
d) As many as required
View Answer
Explanation: The classes can derive from as many classes as required since the multiple inheritance feature is made to combine or group together the functions that are from different classes. This make the derived class stronger in terms of its flexibility.
9. How to overcome diamond problem?
a) Using alias name
b) Using seperate derived class
c) Using virtual keyword with same name function
d) Can’t be done
View Answer
Explanation: To overcome the ambiguity and conflict we can use keyword virtual. This will help us to differentiate the functions with same name that came to last derived class in diamond problem.
10. When multiple inheritance is used, which class object should be used in order to access all the available members of parent and derived class?
a) Derived class object
b) Parent class objects
c) Use Abstract derived class
d) Derive a class from derived class
View Answer
Explanation: The derived class object can access all of its own members. It can also access the available members of the parent classes, because the members are derived into the derived class.
11. If all the members of all the base classes are private then _____________
a) There won’t be any use of multiple inheritance
b) It will make those members public
c) Derived class can still access them in multiple inheritance
d) Compile time error
View Answer
Explanation: The derived class will not be able to access any members of the base classes. Since private member’s are not inheritable. It leads to no use of multiple inheritance.
12. Is it compulsory to have constructor for all the classes involved in multiple inheritance?
a) Yes, always
b) Yes, only if no abstract class is involved
c) No, only classes being used should have a constructor
d) No, they must not contain constructors
View Answer
Explanation: The constructors must be defined in every class. If class is abstract, it won’t have any constructor but other classes must have constructor. Either implicit or explicit.
13. If a class contains 2 nested class and is being inherited by another class, will there be any multiple inheritance?
a) No, only single level inheritance is used
b) No, only multilevel inheritance is used
c) Yes, because 3 classes are involved
d) Yes, because more than 1 classes are being derived
View Answer
Explanation: When a class having nested classes is being derived into another class. It indirectly means a simple class is being inherited to another class. This is single level inheritance.
14. Which members can’t be accessed in derived class in multiple inheritance?
a) Private members of base
b) Public members of base
c) Protected members of base
d) All the members of base
View Answer
Explanation: The private member’s are available for only the class containing those members. Derived classes will have access to protected and public members only.
15. Can the derived class be made abstract if multiple inheritance is used?
a) No, because other classes must be abstract too
b) Yes, if all the functions are implemented
c) Yes, if all the methods are predefined
d) No, since constructors won’t be there
View Answer
Explanation: The derived class must not be abstract. This is because the abstract classes doesn’t have constructor and hence we won’t be having the capability to have instances. This will restrict the use of multiple inheritance.
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