A:天花板对弹簧的拉力和弹簧对天花板的拉力
B:球对弹簧的拉力和弹簧对球的拉力
C:弹簧对球的拉力和球受到的重力
D:球对弹簧的拉力和球受到的重力
有关动植物结构层次的叙述,不正确的是( )
选出相对应的答句。
①Touch your mouth.____ A. Four books.
②How many books?____ B. This is my mouth.
③Here you are. ____ C. Here you are.
④Give me a pencil, please.____ D. One, two. Two pencils.
⑤How many pencils?____ E. Thank you.