若两个相似多边形的周长的比是1:2,则它们的面积比为( )。
1:4
The course that Beijing University offers normally attracts 30 foreign students per year, ________ up
to half will be from America.[ ]
A. in which
B. for whom
C. with which
D. of whom
叉车、装载机工作装置故障多发生在液压系统。