皮皮学，免费搜题
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【单选题】
(2003)第二心音的产生主要是由于:A.
房室瓣开放
B.
房室瓣关闭
C.
动脉瓣开放
D.
动脉瓣关闭
E.
心室壁振动
拍照语音搜题，微信中搜索"皮皮学"使用
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皮皮学刷刷变学霸
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【单选题】If you weigh about 120 pounds, you should spend ______ hours/minutes bowling to burn 1500 calories.
A.
3:48-4:37
B.
7:09-8:20
C.
8:20-10:00
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