26.Even if there is no scientific proof yet ______ secondhand smoke causes cancer, there is no reason why nonsmokers should be forced to take this risk.
A.which | B.that | C.when | D.Where |
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26.Even if there is no scientific proof yet ______ secondhand smoke causes cancer, there is no reason why nonsmokers should be forced to take this risk.
A.which | B.that | C.when | D.Where |