Choose the option that is the passive form of the sentence.

They considered it an impressive building.

It was considered to be an impressive building.

The correct option that is the passive form of the sentence is It was considered to be an impressive building.

The other options are incorrect because:

• It can be consider to be an impressive building is in the active voice.
• It was considering to being an impressive building is grammatically incorrect. The verb "to consider" is followed by a gerund, but the phrase "was considering to being" is not a gerund.
• It is considered to be an impressive building is in the present tense, while the original sentence is in the past tense.