下列哪项不是超过了承载能力极限状态（）。
A、结构作为刚体失去平衡
B、结构变为机动体系
C、结构构件丧失稳定
D、结构局部受压破坏
参考答案：D
—I called you yesterday evening, but there was no answer.
—Oh, I'm sorry. I _______ dinner at my friend's home. [ ]
A. had
B. was having
C. have had
导致下图历史现象出现的根本原因
A．自然灾害频繁
B．急躁冒进的左倾错误
C．中苏关系恶化
D．大跃进和人民公社化运动
