Please pick it up.为什么it要放pick up的中间

look at the paper on the floor,please pick it up 还是 pick them up?

9.Please pick ______ the pen on the ground _____ me 空格了填哪两个介词and
5.They were at school ________ 10:25.
with,for,out,up,of,at,in,on,by,down
1.There is a big apple tree in front ______ my house.
2.I had a big lunch _______ my parents.
3.It‘s time for blowing _______ the candles.
4.Jump up and ________ ten times next to your seat.
6.My father goes to work ______ bike every day.
7.Stand _______ a line,please.
8.They played football _______ Friday afternoon