泊松分布接近正态分布的条件是（）
A.μ=nπ
B.μ≥20
C.μ=0.5
D.n很大且π接近0
E.n很大且π接近0.5
参考答案：B
He tried his best to change it but it didn't at all. [ ]
A. work
B. play
C. work at
D. work on
什么叫农业气象灾害？
