We have been in the school ______ three years ago and Mrs. Lee Has taught us English_______ three years.
A:since; since
B:for; since
C:since; for
D:for; for
如图所示,用两食指同时压铅笔两端,左手指受到的压力为F1,压强为p1,右手指受到的压力为F2,压强为p2,下列说法正确的是()
深圳市的市花勒杜鹃,关于构成一株勒杜鹃花的结构层次由小到大的排列顺序,正确的是( )
关于我国青藏高原的叙述,正确的是