The sentences given given with blanks are to be filled with an appropriate word(s). Four alternatives are suggested for each question . For each question, choose the correct alternative .
Do your best and we'll back you..........

Options

A. on
B. in
C. out
D. up

Answer

D

Explanation

back up (Phr.V.): support
back out (Phr. V.) : to withdraw from something before completion
Here, up is the right option.