1972年尼克松访华被称为“破冰之旅”。对此理解准确的是 [ ]
A、结束了中美对峙状态
B、促进了中美的经济贸易
C、改变了世界的政治格局
D、开始了中美的军事合作
答案:A
I’ve already forgotten you bought the dictionary.
A.that it was when
B.that was it when
C.when was it that
D.when it was that
渐开线上各点的曲率半径()
A.不相等
B.相等
C.无规则变化
D.等于零