The correct passive form of the given sentence is:

☀ Is the remaining chapter being completed by you?

Let's break down the options:

1. Is the remaining chapter being completed by you? (Correct) This sentence correctly uses the passive voice and conveys the same meaning as the original sentence. It uses the correct form "being completed" to indicate an ongoing action in the passive voice.

2. Are the remaining chapter being completed by they? (Incorrect) This option uses the incorrect pronoun "they" instead of "you." The correct form should use "you" to indicate the subject in the passive voice.

3. Is the remaining chapter is being completed by them? (Incorrect) This option includes an unnecessary repetition of "is." The correct form should only have "is" once, as shown in option 1.

4. Are the remaining chapter are being completed by you? (Incorrect) This option uses "are" twice, which is grammatically incorrect. The correct form should only have "are" once, as shown in option 1. Additionally, it uses "chapter are," which is not the correct subject-verb agreement. The correct form should use "chapter is," as in option 1.