．—Are you sure of this evening’s performance, Kate?   

—______. I’m well prepared.

A．I hope so.      B．It’s hard to say.   C．Sure, I am.  D．I’m afraid not.

[　　]

Are you carrying too much on your back at school? I’m sure lots of children of your age will, say "Yes". Not only the students in China have this problem, but children in the United States also have heavy school bags.
Doctors are starting to worry that younger and younger students are having back and neck problems as a result of schools bags being too heavy for them.
"It’s hard for me to go upstairs with my bag because it’s so heavy, "said Rick Hammond, an 11-year-old student in the US.
Rick is among students who have common school bags with two straps(带子) to carry them, but many other students choose rolling(有滚轮的)bags.
But even with rolling bags, getting up stairs and buses is still a problem for children. Many of them have hurt their backs and necks because of the heavy school bags.
But how much is too much? Doctors say students should carry no more than 10% to 15% of their own body weight(重量).
Scott Bautch, a back doctor, said children under Grade 4 should stay with 10 % . But it is also important that older children don’t stay with over 15 %, because their bodies are still growing. "Children are losing their balance(平衡) and falling down with their school bags, "he said.
Parents and teachers are starting to tell children to only take home library books they will be reading that night. Some teachers are using pieces of paper or thin workbooks for students to take home.
One of the best answers is, as some children said, to have no homework at all!
【小题1】 From the passage we can know that      .