根据煤分子结构可大致判断煤的变质程度（）是褐煤的特征。
A.羟基
B.羰基
C.羧基
D.苯酚基
参考答案：C
All his time _______research on Chinese history, he has no time for outdoor activities.
A．devoted to do
B．devoted to doing
C．devoting to doing
D．is devoted to doing
女性，21岁，左颈部扪及2cm直径大小肿块，131I扫描显示"温结节"(硒)甲状腺显影示结节矩无放射性浓聚，B超示肿块为实质性。诊断为
A．甲状腺癌
B．甲状腺腺瘤
C．颈部淋巴结炎
D．甲状腺舌管囊肿
E．囊状淋巴管瘤
