问题
选择题
About _______ gene-targeting drugs are already in testing pipeline. It won’t be long ______ they are put into effect.
A．two dozen; before
B．two dozens; that
C．two dozens of; before
D．dozens; that
答案
答案：A
考查数词及连词。dozen前加数词，后不可加of；it be … before …在……之前有一段时间。根据句意选A。