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 (The accountant) + verb (took) + object (the money) + prepositional phrase (from the the customer) changes to:

'New subject (The money) + verb (was taken) + by + new object (the accountant) + prepositional phrase (from the the customer).

The passive form of 'took' in the simple past tense is 'was/were taken'.

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

Option A: The tense of the given sentence is in past, whereas here the verb 'is' expresses the simple present tense. The voice of the sentence has changed, but the tense still remains the same.

Option C: The meaning of the sentence is vague: 'the customer was taken the money' which does not have a complete meaning.

Option D: 'Had been taken' expresses the past perfect tense. But the sentence is in the simple past tense.