Final answer:
Whether a base class assignment operator is called on a derived class object depends on if the derived class has its own assignment operator. If it does not, the base class operator is used; otherwise, the derived class operator is used.
Step-by-step explanation:
Whether a base class assignment operator is called on a derived class object depends on whether the derived class has its own assignment operator. In C++, if the derived class (Class B) does not explicitly override the assignment operator, the base class (Class A) assignment operator will be used. However, if class B has its own implementation of the assignment operator, that will be used instead.
In most cases, it's advisable for the derived class to implement its own assignment operator to ensure that all the properties of the derived class are correctly copied over. This is important to ensure proper object slicing does not occur, where only the base part of a derived object is assigned, potentially leading to loss of data related to the derived part.
If class B has not provided its own assignment operator, then answer a would be correct; the assignment would use class A's assignment operator. If class B has defined its own operator, then answer b would be correct; it would use class B's assignment operator.