Question

One should keep one's promice change in to passive voice

Answer 1

promise should be kept by one

Answer 2

How do I say, “One should keep one's promise” in passive form?

The question is ‘One should keep one's promise'.

The above setence means that every body should keep his/ her promise. It doesn't mean about one or some persons.

So, the answer is ( Promises should be kept ) but ( by one) should not be used.

AV: One should love one's parents. PV: Parents should be loved.

One should respect one's teacher. PV: Teachers should be respected.