Choose the correct passive voice: They are building a new hospital.

The original sentence, "They are building a new hospital," is in the present continuous active voice. To transform it into the passive voice, we need to follow a specific structure:

• The object of the active sentence becomes the subject of the passive sentence. Here, "a new hospital" is the object.
• The auxiliary verb "to be" is used in the same tense as the active verb, followed by "being" for continuous tenses. Since the active sentence uses "are building" (present continuous), the passive form will use "is being" (because "a new hospital" is singular).
• The main verb is changed to its past participle form. The past participle of "build" is "built."

Combining these elements, "A new hospital is being built" correctly forms the present continuous passive voice. Option B, "A new hospital was built," is past simple passive. Option C, "A new hospital builds," is present simple active. Option D, "A new hospital is built," is present simple passive. Therefore, option A is the only correct choice that maintains the original tense and meaning in the passive voice.