题型:问答题 简答题 在空间中,用a,b,c表示三条不同的直线,γ表示平面,给出下列四个命题:①若a∥b,b∥c,则a∥c; ②若a⊥b,b⊥c,则a⊥c;③若a∥γ,b∥γ,则a∥b; ④若a⊥γ,b⊥γ,则a∥b;其中真命题的序号为______. 查看答案
题型:问答题 简答题 Teterboro is the same airport where a plane took off earlier this morning before colliding (碰撞)with a sightseeing helicopter over the Hudson River.A.whereB.asC.thatD.which 查看答案