进排气门的重叠角出现在下列哪个描述附近（）
A.压缩上止点
B.排气上止点
C.做功下止点
D.进气下止点
参考答案：B
The third women’ s conference ______ in the USA this summer talked about women’s rights in the developing countries.
A．to be sponsored
B．sponsoring
C．sponsored
D．was sponsored
影响核酸保存的关键因素是什么？怎样保存核酸制品？
