一个长方形的长是7厘米，宽是4厘米，它的周长是多少厘米？
（7+4）×2，
=11×2，
=22（厘米），
答：它的周长是22厘米．
The Gulf of Mexico (墨西哥湾) is being polluted seriously. That has affected _______ several hundred kinds of
sea animals there. [ ]
A. at least
B. at once
C. at birth
D. at times
表达式26/4*3的值是 ______ 。
A．1
B．2
C．18.75
D．18
