Steven is the ________ student in his class. He is good at all the lessons and ready to help others. [ ]

A. better

B. best

C. worse

D. worst

巴比妥类药物分子结构中因含有酰亚胺基团，因而可于碱性介质中加热水解，产生能使红色石蕊试纸变蓝的气体。该气体应为

A．乙二胺
B．二氧化碳
C．二乙胺基乙醇
D．氨气
E．乌洛托品