An action in a sentence can be represented in two ways, namely active and passive voice.

The passive voice always uses the past participle form of the main verb irrespective of any tense. Only the auxiliary verbs depend upon the sentence given in active voice.

The correct answer is B)My umbrella has been stolen by somebody.

Option B is correct as to use the word steal, the subject remains at its place and been is added after has and before stolen.

The other options are wrong as been is not added, is cannot be used, and somebody cannot be used in the beginning( because of the given verb).