渴望被别人信任、承认和重视，是少年儿童最大的心理需求。（ ）
A、正确
B、错误

单项选择题Which one of the following four statements is true? A、An induced electric field is caused by a stable magnetic field. B、An induced electric field is caused by the motion of charges. C、A displacement current is the rate of change of charges. D、A displacement current is caused by a time-varying electric field.

单项选择题对于M次观测d和N个模型参数m之间的离散线性关系d=Gm，当r=N＜M时，Gm=d是超定方程。（ ）