从力学角度考虑，理想的桩冠直径为（）。
A.根径的1/2
B.根径的2/3
C.根径的1/3
D.根径的3/4
E.尽量大
参考答案：C
短文改错（共10小题；每小题1分，满分10分）
假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，要求你在错误的地方增加、删除或修改某个单词。
增加：在缺词处加一个漏字符号（^），并在其下面写出该加的词。
删除：把多余的词用斜线（\）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。[
注意：
1．每处错误及其修改均仅限一词。
2．只允许修改10处，多者（从第11处起）不计分。
In order to make best of learning materials, the Student’s Union of our school is planning an
activity. The school – leavers are called on to give away our used books, newspapers or magazines to the student in the lower grades. The idea, that is intended to promote friendship and encourage a low – carbon lifestyle, are highly praised and supported by the teachers and students alike. The activity will be hold on the first floor of the school library and so it will last eleven days, from June 10 to 20. as student, I am strong for the activity because it is very meaningful and helpful. I hope that this kind of activity would continue every year for the future.
由于老胡失业而引发其妻子临时就业的这种效应被称为( )。
A．灰心丧气的工人效应
B．附加的工人效应
C．收入替代效应
D．劳动力市场效应
