心动周期中从房室瓣关闭到开放的时间约相当于()。
A.心房收缩期+心室等容收缩期
B.心房舒张期
C.心室收缩期
D.心室舒张期
E.心室收缩期+等容舒张期
参考答案:E
世界最大的热带雨林区位于( )
A.亚洲
B.南美洲
C.欧洲
D.南极洲
My mother often cooks _____ in many different ways because I like them very much. [ ]
A. chicken
B. meat
C. beef
D. potatoes