Change the voice of “One should keep one’s promise”.

1. One’s promise should be kept
2. A promise should be kept.
3. One’s promise should be kept by one.
4. Promise should be kept

Explanation: One, Nobody, No one, Everyone, Everybody, Somebody ইত্যাদি Indefinite pronoun যুক্ত active voice থেকে passive voice এ রূপান্তরের সময় Indefinite pronoun গুলো উঠে যায়। যেমন-
Active: One should keep one’s promise.
Passive: A promise should be kept.

Active: Nobody knows him here.
Passive: He is not known here.