A. We has to get to some serious work in order to sort out the untidy office.
REJECTED - Literally reading it implies that the the serious work is in a different place to which we need to travel. Illogical.
The use of 'We has' is also wrong.
B. We had to get down to a serious workout in order to sort out the untidy office.
REJECTED - workout is wrong. It refers to the the physical exercise done in a gym.
C. We had to get to some serious work down in order to sort the untidy office.
REJECTED - Literally reading it implies that the the serious work is in a different place to which we need to travel. Illogical.
D. We had to get down to some serious work in order to sort out the untidy office.
RIGHT ANSWER
E. We had to get to some serious work in order to sort the untidy office out.
REJECTED - Literally reading it implies that the the serious work is in a different place to which we need to travel. Illogical.