air pollution is threatening the health of people in urban areas(by)用preaent cotinuous passive

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air pollution is threatening the health of people in urban areas(by)用preaent cotinuous passive

The health of people in urban areas is being threatened by air pollution.

the health of people in the urban areas is threatened by the air pollution.

The health of people in urban areas is being threatened by air pollution .
现在进行时的被动结构是:am/is/are (not) being done