皮皮学，免费搜题
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【单选题】
产生第二心音的主要原因是A.
心房肌舒缩
B.
房室瓣开放
C.
房室瓣关闭
D.
动脉瓣开放
E.
动脉瓣关闭
拍照语音搜题，微信中搜索"皮皮学"使用
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】The relationship between internal force and stress is that
A.
The internal force is smaller than the stress.
B.
The internal force is the algebraic summation of the stress.
C.
The internal force is a vector and the stress is a scalar.
D.
The stress is the internal force per unit area.
【简答题】阅读理解。 Basketball players are usually very tall. Because they need to put the ball into the basket. Other sports players may be shorter than them. Short people often have better balance than tall peop...
【简答题】Here are the table tennis players , some____ ____are our old friends.(介词加关系词)
【判断题】The internal force concentration caused by internal force is called stress.
A.
正确
B.
错误
【简答题】Here are the table tennis players, some __ _____ are our old friends.
【单选题】听力原文： Tennis is an international sport and each year there is a regular program of tournaments and championships. Players' performance in these events determines their seeding, or world ranking. If yo...
A.
The Hopman Cup.
B.
The Masters Series.
C.
The Wimbledon Championships.
D.
The ATP Tour.
【单选题】Some tennis players enjoy doing different things off the _________.
A.
champion
B.
tennis
C.
court
D.
fans
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