A rain drop starts falling from a height of 2 km. It falls with a continuously decreasing acceleration and attains its terminal velocity at a height of 1 km. The ratio of the work done by the gravitational force in the first half and the second half of the drops journey is:

1 : 1 and the times of fall of the drop in the two halves is a : 1 (where a > 1)

a : 1 (where a < 1) and the times of fall of the drop in the two halves is 1 : 1

1 : 1 and the times of fall of the drop in the two halves is a : 1 (where a<1)

a : 1 (where a > 1) and the times of fall of the drop in the two halves is 1 : 1