Allcargo Logistics interview question

Technical Interview It was based on the .Net programming they told me to 1) write a program to reverse the string 2) write a program for Fibonacci series OOPS concept - abstraction -encapsulation -polymorphism -questions based on inheritance like how runtime objects get executed eg- public class a{} public class b{} while creating object in main method what will be the output- a c= new b(); answer is - the methods of A get the access -virtual and override concept -pointer based question , -abstract class and interface