The bark of some species of oak trees yields substance used in ____ leather.

The bark of some species of oak trees yields substance used in ____ leather.

A.treating

B.to treat

C.its treatment

D.it treats

答案及解析： A

解析：

介词后面只能跟动词的v+ing形式。不必十分清楚这句话的意思，便可选定A． treating。而因为缺少介词of引导的短语of leather，故不能使用C． its treatment中的名词treatment构成词组：in treatment of leather（最好说：in leather treatment）。