If A alone can complete a work in 20 days and B alone can complete the same work in 30 days, then which of the following statement(s) is/are correct?
I. Ratio of efficiency of A and B is 3 : 2.
II. Working together A and B can complete the same work in 12 days.

A

Neither I nor II

B

Both I and II

C

Only II

D

Only I