请教大家一道语法题，谢谢大家了！

Amelia_He

34. Xanthines have both good and bad effects on the body, and these effects are

                             A

generally
            determined on the size and regularity of dosage.

   B          C                           D

 

 

答案选C。我不太明白！能帮我解答一下吗？

 

wycg

我觉得那个C要划线到on, 那个on 用的不对.要用by.

wl_xiao

同意

Amelia_He

哦，是这样啊！谢谢楼主了！