Help! I don't understand this question (please explain with a diagram)

A stone (A) is dropped from rest from a height h above the ground. A second stone (B) is simultaneously thrown vertically up from a point on the ground with velocity "v". The line of motion of both the stones are the same. The value of v which would enable stone B to meet stone A midway (at midpoint) between their initial positions is: (correct answer - option 3)

1. 2gh
2. 2√(gh)
3. √(gh)
4. √(2gh)