Find the part of the given sentence that has an error in it. If there is no error, choose ‘No error’.

By lowering rooftop surface (1)/ temperatures, green roofs (2)/ can be kept cooler (3)/. No error (4)

The correct answer is '4'.

Key Points

• The given sentence contains no error.
• If V3 appears after the verb 'to be', it can function only as a passive like the example (to be removed).
• Thus, the sentence is in passive voice.
• We use the past form of the verb in the passive voice and the past form of the verb 'keep' is 'kept'.
• Thus, the sentence contains no error.

Hence, the correct answer is option (3).