278.9去掉小数点后，这个数扩大了______倍．
278.9去掉小数点后是2789，小数点向右移动一位，这个数就扩大10倍．
故答案为：10．
_____ Browns are going shopping this Saturday. They are going to buy _____useful umbrella.
A．/; a
B．The; a
C．/; the
D．The; an
Mary, ____ late for school again![ ]
A. isn't
B. doesn't
C. doesn't be
D. don't be
