vaccines(疫苗)arecomplexbiologicproducts. strongman...
来源：语文精选馆 2.59W
问题详情：
vaccines (疫苗) are complex biologic products. strong management and if not correctly, vaccines can lose same of their effectiveness.
A. requiring; handled B. requiring; handling
C. required; handling D. required; handled
【回答】
A
知识点：非谓语动词
题型：选择题
