B - 20 seconds.

A rectangle is defined as a quadrilateral with 4 right angles. Looking at the first choice, you know it's insufficient because you think of a rhombus--it could be a rectangular (square) or non rectangular (non square) rhombus.

Looking at the second choice, recall that the sum of the angles must be 360 no matter what the shape of the quadrilateral. So if the max each angle can be is 90, that would add up to 360. So no angle can be less than 90 either, so each angle is 90, and hence, you have a rectangle.