单项选择题 对于某线性电阻元件R,  无论其电压U与电流I的参考方向如何标出，其伏安特性VAR总为： A、正确 B、错误

单项选择题 The author most likely mentions the physical appearance of the impoverished child in the last paragraph in order to: A、criticize a social upbringing that would allow a child to suffer in such a way. B、contrast the poverty of the second child with the privilege of the first. C、intensify the reader's sympathetic reaction toward the child. D、identify the cause of the child's poverty. 无解析

单项选择题 立体裁剪起源于哪里？ A、欧洲 B、亚洲 C、非洲 D、美洲