对某边观测4测回，观测中误差为±2cm，则算术平均值的中误差为( )。
A．±0.5cm
B．±1cm
C．±4cm
D．±2cm
参考答案：B
The great photos in the museum _____ people a lot last week. [ ]
A. had interest in
B. were interested by
C. interested
D. were interested in
（2011年四川绵阳，17题）相同质量的Mg、Fe分别与稀盐酸作用，产生H2的质量m（H2）与加入稀盐酸的体积V（稀盐酸）关系如下图所示，其中正确的是
