Select the passive form of the given sentence.

They are constructing a residential youth hostel.

A residential youth hostel is being constructed by them

The correct passive form of the given sentence is A residential youth hostel is being constructed by them.

The active voice of the sentence is They are constructing a residential youth hostel. This sentence is in the present progressive tense, which is used to describe an action that is happening now. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the present participle of the main verb. In this case, the subject of the active sentence is "they" and the main verb is "construct." The present participle of "construct" is "constructing." So, the passive form of the sentence is A residential youth hostel is being constructed by them.

The other options are incorrect because:

• A residential youth hostel is constructed by them. is in the simple present tense, while the original sentence is in the present progressive tense.
• A residential youth hostel was constructed by them. is in the simple past tense, while the original sentence is in the present progressive tense.
• A residential youth hostel has been constructed by them. 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 constructing the residential youth hostel is not something that has happened yet.