国家质检总局对向中国输出水果的国外果园实行( )。
A.备案登记制度
B.质量许可制度
C.注册登记制度
D.强制性认证制度
参考答案:C
The _____ look in his face suggests that he is happy. [ ]
A. exciting
B. excited
C. excite
D. excitement
简答案影响汽轮机胀差变化的原因。