— Would you like to come to have dinner this evening?
— I'd like to _______ I'm free.
A:and
B:if
C:but
D:so
物质
A
B
C
D
微观示意图
设随机变量X~N(2,4),则D(12X)的值等于( )
0.08= ____ 0.63=____ 0.5=____ 0.312=____
关于生态系统,下列说法错误的是( )