女性生殖系统最常见肿瘤为（）
A.子宫颈癌
B.子宫内膜癌
C.卵巢癌
D.子宫内膜平滑肌肉瘤
E.子宫平滑肌瘤
参考答案：E
_____ lacking in money, his parents, making their living by working abroad, managed to send him to
a key middle school.[ ]
A. Because
B. When
C. As
D. Though
对比下 * * 个反应式：
O+O====O2；ΔH＝－497 kJ·mol-1
N+N====N2；ΔH＝－948 kJ·mol -1
Cl+Cl====Cl2；ΔH＝－242 kJ·mol-1
可以得出的结论是( )
A．氮元素不能形成同素异形体
B．在常温下，氮气比氧气、氯气要稳定得多
C．氮的非金属性最强
D．氮、氧、氯的单质在自然界都能稳定存在
