题目内容：

Have you ever noticed how much the number twelve is used? A ruler that is a foot long has twelve inches. A yardstick(尺码) has three times twelves inches, or thirty-six inches.

On a canlender you will see twelve months in each year. A clock face is numbered from one to twelve for the hours. The time span from noon to midnight is twelve hours; from midnight to noon there are twelve more hours. Each day is two times twelve, or twenty-four hours long.

We buy eggs by the dozen, which means twelve at once. Sometimes we buy other things by the dozen. The stores sell different things by the dozen. In a store you may have seen a dozen pencils held together by a paper wrapping or a dozen oranges in a sack. Stores also buy things in lots of twelve dozens, or by the gross（罗，12 打） . One gross consists of twelve dozens, or one hundred and forty-four items.

1.An outside cover is a _______.

A. bag            B. sack          C. number          D. wrapping

2._______ means a space of time.

A. Span            B. Gross        C. Room           D. Canlender

3.A foot-long ruler has _______ inches.

A. six              B. twelve       C. twenty-four        D. thirty-six