Up to now air pollution _____(do)great harm to human beings.

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Uptonowairpollution_____(do)greatharmtohumanbeings.Uptonowairpollution_____(do)greatharmtohumanbeing

Up to now air pollution _____(do)great harm to human beings.
Up to now air pollution _____(do)great harm to human beings.

Up to now air pollution _____(do)great harm to human beings.
up to now =so far,
pollution 是不可数名词.has done

has done
up to now表示迄今为止,可以说是现在完成时的标志,强调了动作对现在的影响.

have done

has done