可引起白血病的生产性毒物有：（）
A.石棉
B.氯乙烯
C.苯
D.苯胺
E.铅
参考答案：C
Qian Xuesen is known as China's "father of space technology" and "king and rockets".
He died _____ October 21 at the age of 98. [ ]
A. in
B. on
C. at
D. of
下列可以进行方法示范的有（）
A.幼鸡鉴别
B.棉花整枝
C.果树修剪
D.作物品种
E.新产品
