Question

If EFGH is a parallelogram, then ___________________.

Answer 1

B, it might be a rhombus.

This is because it could be a square or rectangle as both are also parallelograms. 

Answer 2

Some parallelograms are also a rhombus.
So that's why the answer is choice B. 

Note: Any rhombus is a parallelogram, but the other way around isn't true. For example, a rectangle that isn't a square is also not a rhombus. Any rectangle is a parallelogram. Not all parallelograms are rectangles.