生活中区分羊毛和涤纶的方法正确的是（ ）
A．观察颜色
B．灼烧闻气味
C．放入食醋中
D．浸入肥皂水中
答案：B
鸡兔同笼，有12个头，40只脚，算一算，笼子里有几只鸡，几只兔？
- I have coffee to refresh myself recently.
- Is that so? If you _______, make sure you limit it to one cup a day.[ ]
A. shall
B. may
C. can
D. must
