种子萌发需要的环境条件是适宜的____、一定的水分和充足的____.
— What is 16 ____ 4?
— It's 4. 2 ____ 2 is also 4.
已知随机变量ξ服从正态分布N(0,σ2),若P(ξ>2)=0.023,则P(-2≤ξ≤2)=( )