What is nextjs? How can we use it?

Answer the following short questions. Your answer should be precise.

1. Can we declare base class constructor or destructor as virtual if yes then why we want to do?
2. How we can declare a class as abstract and why we need abstract classes?
3. Why we cannot able to create objects of abstract classes give reasonable justification of that.   

This question is related to Object orientated programming in c++

1. Can we declare base class constructor or destructor as virtual if yes then why we want to do?

In Machine, How did we teach the model to exit early in training in certain cases?

A.  We changed the number of epochs

B.  We changed the learning rate

C.  We added a condition number

D.  We added a callback function