钠泵转运Na+、K+属于
A．单纯扩散B．载体中介的易化扩散C．通道中介的易化扩散D．主动转运
参考答案：D
下列保护地球宇宙环境的做法，正确的是
①限制空间垃圾的产生 ②向宇宙空间多发射各种航天器
③清除太空垃圾 ④宇宙空间具有无限性，不必关心空间垃圾 [ ]
A、①②
B、①③
C、①④
D、②③
I always remember what she ______ when I saw her for the first time. [ ]
A. does
B. is doing
C. was doing
D. has done
