露地花卉播种出苗后，幼苗长出（）片真叶出现拥挤时，即行移植。
参考答案：2-5
You are very young. You must remember _______. [ ]
A. what your father said
B. what your father say
C. what does your father say
设随机变量X服从λ=2的泊松分布，则P（X≤0）=（）。
A．e-2
B．2e-2
C．2e-2
D．7e-2
