True or false (Java)?

1. All elements of an array are of the same type.

2. Arrays cannot contain strings as elements.

3. Two-dimensional arrays always have the same number of rows and columns.

4. Elements of different columns in a two-dimensional array can have different types.

5. A method cannot return a two-dimensional array.

6. A method cannot change the length of an array argument.

7. A method cannot change the number of columns of an argument that is a two-dimensional array.