小学阶段的儿童思维结构的特点是( )。
A．未掌握守恒B．思维不具有可逆性C．理解补偿关系D．相对性
参考答案：C
(2013·江苏南通市二模)We ________ have hurried all the way to the airport — the flight was called off because of the foggy weather.
A．mustn't
B．couldn't
C．needn't
D．wouldn't
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