One must keep one's promises.
A. One's promises are kept.
B. Ones promises must kept.
C. Ones promises were kept.
D. One's promises must be kept.
Answer: Option D
Solution (By Examveda Team)
One's promises must be kept.The subject 'One' has to be replaced with 'One's promises' keeping the tense same.

One's promises must be kept by one
ky yah b sae hai???