Right Answer is: B
The given sentence is in active form of simple past tense. The structures for active/passive voices are:
Active: Subject + verb (IInd form) + object.
Passive: Object + was/were + verb (IIIrd form) + by + subject.
So, with the help of the above structures, we can convert the given sentence into passive voice:- The thief was arrested.
Hence, option B is the correct answer.