The passive form of the sentence 'One must keep one's promises' is -

A One's promises are kept

B One's promises must kept

C One's promises were kept

D One's promises must be kept

Correct Answer: Option D

voice change করতে object হয়ে যাবে sub+must be+verb এর past form+sub হয়ে যাবে object.
One's promises must be kept