测定水泥体积安定性的方法为沸煮法,包括()和()两种。
参考答案:雷氏法;试饼法
某化合物由C、H、O三种元素组成,其红外光谱图中有C-H 键、O-H键、C-O键的振动吸收,该有机物的相对分子质量是74,则该有机物的结构简式是 [ ]
A.CH3CH(OH)CH3
B.CH3CH2OCH3
C.CH3CH2CHO
D.CH3CH2CH2CH2OH
If you follow the doctor's advice, you'll look and feel much better ______. [ ]
A. at no time
B. at times
C. in no time
D. for a time