I have two grammars, ______are of great use.
A. all of which B. either of which C. both of that D. both of which
I have two grammars, ______are of great use.
A. all of which B. either of which C. both of that D. both of which
D
主句中的two表明不能选A.从句中的are表明不能选B. both of which用来引导非限制性定语从句.