What can trees do _________ us ?They can _________ harmful gases and produce oxygen .

题型：单选题题类：常考题难易度：普通

What can trees do _________ us ?
They can _________ harmful gases and produce oxygen .

A、helping , take in B、to help , take in C、helping , take out D、to help , take care

举一反三

- Because my car broke down on the way.

— Sorry, I'm new here.

Which is the faster way {#blank#}1{#/blank#} {#blank#}2{#/blank#} to Tianjin, by plane or by train?

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