— The little boat is ______ safe. Don't you think so, Mike ?
— No worries! I've been on this boat dozens of times.
A:something but
B:nothing but
C:anything but
D:everything but
以下不能说明光在同种物质中沿直线传播的现象是( )
①某寻呼台一小时内收到的寻呼次数X;②在(0,1)区间内随机的取一个数X;③某超市一天中的顾客量X。其中的X是离散型随机变量的是( )
长江和黄河上游都具有的共同特征是( )