The correct passive form of the given sentence is He was taught English by his elder sister.

The active voice of the sentence is His elder sister taught him English. This sentence is in the simple past tense, which is used to describe an action that happened in the past. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "he" and the main verb is "teach." The past participle of "teach" is "taught." So, the passive form of the sentence is He was taught English by his elder sister.

The other options are incorrect because:

• His elder sister is taught English by him. is in the passive voice, but the subject of the sentence is "his elder sister," which is not the one being acted upon. The subject of the sentence should be "he."
• He has been taught English by his elder sister. is in the present perfect tense, which is used to describe an action that has happened in the past but is still relevant to the present. The action of teaching him English is not something that is still relevant to the present.
• He is being taught English by his elder sister. is in the present progressive tense, which is used to describe an action that is happening now. The action of teaching him English is not something that is happening now.