（）叶轮直径能增大泵的流量。
A.减小
B.增大
C.不变
D.无法通过改变
参考答案：B
观察右面几组勾股数，①3，4，5；②5，12，13；③7，24，25；④9，40，41；并寻找规律，请你写出有以上规律的第⑤组勾股数：______，第n组勾股数是______．
Sit down, Emma. You will only make yourself more tired, ________ on your feet.[ ]
A. to keep
B. keeping
C. having kept
D. to have kept
tired, ________ on your feet.[ ]