X_o  and v_o  are 0 for this problem.

X = 0.5 a t²  

          2X                  2 x 19.6 m
t = (---------) ^1/2 = (-----------------) ^1/2 =  2.00 s
            a                    9.80 m s ^-2 

v = v_o  +  at  =  0 m/s  +  9.8 m/s x 2 = 19.6 m/s

The Correct Answer is B.