If you define a destructor, are you required to define an operator '=' and a copy constructor?

a. yes, that is the rule of three.
b. yes, doing so is required by the compiler.
c. no, but doing so is often the appropriate decision.
d. no, but failing to do so will cause a memory leak.

a. Yes, that is the Rule of Three.

Explanation:

A destructor can be defined as a special member function of the class that is used to deallocate the memory assigned to the data members of the class after the created objects of the class go out of scope. If we define a destructor or a copy constructor or an operator "=", we need to include the definition of the other two in the class according to the rule of three.

This is because the compiler copies and copy assign the objects of the class in various situations and if these functions are not present, they are implicitly created and called.