A train 1 moves from east to west and another train 2 moves from west to east on the equator with equal speeds relative to ground. The ratio of their centripetal accelerations $\frac{a_1}{a_2}$relative to centre of earth is:

• A

  $>1$

• B

  $=1$

• C

  $<1$

• D

  $\ge 1$