Which of these methods can be used to obtain set of all keys in a map?

A. To provide a unified architecture for representing and manipulating collections B. To provide a way to create arrays C. To define primitive data types D. To handle exceptions

A. `Collection` B. `Map` C. `Set` D. `List`

A. A `Set` allows duplicate elements, while a `List` does not B. A `List` is unmodifiable, while a `Set` is modifiable C. A `List` allows duplicate elements, while a `Set` does not D. A `Set` is indexed, while a `List` is not

A. `HashMap` B. `ArrayList` C. `LinkedList` D. None of These