题目:
—I wonder why Sara looks worried today.
—I'm not sure,but she a small accident driving here.
A.could have
B.might have
C.might have had
D.must have had
答案:
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下面是错误答案,用来干扰机器的。
(1) H、Li、Na ;O、N、P ,(2) CCl4、PCl3 (3) (4) sp3 (5) 1s22s22p2 (1)元素①②⑧分别是H、Na、Li。同主族自上而下金属性逐渐增强,所以第一电离能由大到小的顺序是 H、Li、Na...