甲、乙、丙三架观光电梯,甲中乘客看一高楼在向下运动,乙中乘客看甲在向下运动.丙中乘客看甲、乙都在向上运动.这三架电梯相对地面的运动情况可能是( )
A:甲向上、乙向下、丙不动
B:甲向上、乙向上、丙不动
C:甲向上、乙向上、丙向下
D:甲向上、乙向上、丙也向上,但比甲、乙都慢
用所给单词填空
(1)Sometimes we ____ food at home. (2)I ____ drinking milk. (3)We often ____ CCTV news at 7:00 in the evening. (4)I ____ the Internet once a day.(5)The results for “read English books”____ fun.(6)How often do you ____ to the English corner? (7)Everyone will____ you if you need any help.(8)The sun ____ once a day. (9)Walking can ____ you in good health.(10)I____ nine hours every night.
下面4个算式中,结果一定等于14的是( )(其中□=2△,△≠0)
已知| a→ |=1,| b→ |= 2 ,且 a→ ⊥( a→ ﹣ b→ ),则向量 a→ 与向量 b→ 的夹角是____.