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已知a、b、c是直线,β是平面,给出下列命题: ①若a⊥b,b⊥c,则a∥c; ...
已知a、b、c是直线,β是平面,给出下列命题:
①若a⊥b,b⊥c,则a∥c;
②若a∥b,b⊥c,则a⊥c;
③若a∥β,b⊂β,则a∥b;
④若a与b异面,且a∥β,则b与β相交;
⑤若a与b异面,则至多有一条直线与a,b都垂直.其中真命题的个数是( )
A.1
B.2
C.3
D.4
考点分析:
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