Read the following statements about sets

1. If A and B are sets then A + B denotes union of sets A and B.
2. The union of A and B is that set whose elements are in either A or B or both.
3. If A and B are sets, then difference of sets A and B is denoted by A - B.
4. A - B in the set obtained by removing elements of A from B.

Which of the above are true?