用下列词语造句

①俊秀

②专注

⑴Where are your parents?____                           A. Yes, I'd like some fruit.

⑵Is your brother sleeping in the room?____      B. They are at home. 

⑶Can I help you?____                                         C. She's playing the piano.

⑷Would you like some fruit?____                       D. No, I'm not.

⑸Can you see the red light?____                        E. She's singing.

⑹What is Helen doing?____                                F. Yes, please.

⑺Are you busy?____                                           G. No, I can't.

⑻What is she doing in the music room?____     H. No, he isn't.

如图，粗糙水平面上a、b、c、d 四个相同小物块用四根完全相同的轻弹簧连接，正好组成一个等腰梯形，系统静止．ab之间、ac之间以及bd之间的弹簧长度相同且等于cd之间弹簧长度的一半，ab之间弹簧弹力大小为cd之间弹簧弹力大小的一半．若a受到的摩擦力大小为f，则（   ）