A：y=-1(x>0)
B：y=+1(x>0)
C：y=-1(x R)
D：y=+1 (x R)
选出合适的应答语。
A. You should go to bed early.
B. You should wear a sweater.
C. She should tell the teacher and go to see the doctor.
D. You should tell your mother.
E. You should take it to see the vet.
F. You should help her do some chores.
—OK. Don't worry. I can ____________ at 6:00 in the morning.
过滤是化学实验中的一项重要基本操作,其中不需要使用的仪器（）
