A.               B.              C.            D.

A.1个                B.2个             C.3个             D.无穷多个

A.140种             B.84种               C.70种             D.35种

A.0                 B.2                   C.4                D.6

A.129种            B.148种               C.165种           D.585种

①若m∥α,n∥β且α∥β,则m∥n;

②右m⊥α,n⊥β且α⊥β,则m⊥n;

③若m⊥α,n∥β且α∥β,则m⊥n;

④若m∥α,n⊥β且α⊥β,则m∥n.

其中真命题的序号是(    )

A.①②             B.③④                 C.①④             D.②③

A.若m⊥α,m⊥n,则n∥α                     B.若m∥α,n∥α,则m∥n

C.若mα,n∥α,则m∥n                     D.若m、n与α所成的角相等,则m∥n

A.-540                 B.-162               C.162                D.540

A.5 040种                B.720种         C.240种            D.1 440种

A.平行                   B.相交           C.垂直             D.互为异面直线