Two additional foundational building blocks of Objective-C distinct from data and procedure type foundations: _____ and Categories/Extensions?

Name of the root class in Objective-C?

Look at below code and tell what the problem could be:

Look at below code and tell which is correct.

Difference between the unsigned int and the NSUInteger?

The part of an Objective-C class specification that declares its public interface which includes its superclass name & instances variables and public-method prototypes is called:

In which version of Objective-C did the fast enumeration system appear?

A class can conform to only one protocol?

What is a category?

What happens if you release an unretained object twice?

What does Obj-C not support?