下列哪种情况应考虑急性心肌梗死的可能()
A.夜间发生心绞痛
B.卧位型心绞痛
C.缺血性胸痛持续大于30分钟
D.恶化劳力型心绞痛
E.新近发生心绞痛
参考答案:C
甲烷和丙烷混合气体的密度与同温同压下乙烷的密度相同,则混合气体中甲烷和丙烷的体积比是
A.2:1
B.3:1
C.1:3
D.1:1
— Is there a supermarket?
— No, _____. [ ]
A. this is not
B. there isn't
C. it isn't
D. there aren't