What is the key difference between NSDictionary and NSMutableDictionary?

What is foo? -(float)foo;

What's wrong with this code?float x = 5.;

What does ARC stand for?

What best describes class inheritance in Objective-C?

What is different about this function? +(void)doSomething;

Which of the following is a Singleton?

How do you concatenate two NSStrings *foo and NSString *bar to form a new NSString *baz?

What does the "id" type mean?

To have an IOS app Screen Design we used which of the following tool?

What is the method for adding KVO to your app?