The boy is very fat ____ too much food. [ ]
A. So
B. so of
C. because
D. because of
答案:D
SD与SMZ于碱性条件下,可与硫酸铜发生沉淀反应的依据是
A.磺酰氨基上的活泼氢
B.芳伯氨基
C.对氨基磺酰胺
D.杂环氮的碱性
E.苯胺基
带煤气动火需要采取哪些安全措施?