A particle of mass 200 g is dropped from a height of 50 m and another particle of mass 100 g is simultaneously projected up from the ground along the same line, with a speed of 100 m/s. The acceleration of the center of mass after 1 second is

• A

  $10 \mathrm{m}/{\mathrm{s}}^2$

• B

  $\frac{10}{3}\mathrm{m}/{\mathrm{s}}^2$

• C

  Zero

• D

  None of these