If this sentence is changed to passive voice, then the subject is also changed, in order to retain the meaning of the sentence.

So, the object takes the place of the subject and vice versa and the word 'by' is introduced as now the subject receives the action by the object. The verb form of the sentence is also changed from active form to passive.

'Subject (Circumstances) + verb (will oblige) + direct object (me) + infinitive phrase (to go)' changes to:

'New subject (I) + verb (shall be obliged) + infinitive phrase (to go) + by + new object (the circumstances)'

The passive form of 'will oblige' in the simple future tense is 'shall be obliged'.

This can be seen in option B, hence it's the right answer.

(Minor additions like the article 'the' to the word 'circumstances' is acceptable as the voice has been changed.)

Option A: The sentence is still in the active voice, as the verb form 'will oblige' has not been changed. As a result, the meaning has changed.

Option C: The word form of this sentence has changed, and the sentence still remains in active form.

Option D: The sentence must end with the object 'by the circumstances' since the infinitive phrase 'to go' must be as close to the verb as possible and hence not be at the end.