Step 1: Understanding the original sentence.
The sentence expresses a moral duty that a person must keep his or her promises. Step 2: Applying the instruction.
We must begin the sentence with the word Promises.
To do this correctly, we convert the sentence into passive voice. Step 3: Analyzing the options.
(A) is grammatically incorrect.
(B) gives the opposite meaning.
(C) correctly changes the sentence into passive form while keeping the same meaning.
(D) changes the structure and meaning slightly. Step 4: Conclusion.
Hence, the correct rewritten sentence is option (C).