质量相等的蔗糖同时分别投入等量的水中,溶解最慢的是( )
A.将蔗糖直接投入水中
B.将蔗糖研细后投入水中
C.将蔗糖投入水中后加热
D.将蔗糖投入水中并不断搅拌
答案:A
All these gifts must be mailed immediately ________ in time for Christmas. [ ]
A. in order to have received
B. in order to receive
C. so as to be received
D. so as to be receiving
国标法规定测定酒中甲醇杂醇油可用气相色谱法,须用哪种检测器()。
A.热导检测器
B.电子捕获检测器
C.火焰光度检测器
D.氢火焰离子化检测器
E.以是四种都能用