—It is very clean and beautiful _____ it is a bit small.
A:if
B:since
C:unless
D:although
She ____ ____ the customers' complaints ____ every time.
1﹣丁醇和乙酸在浓硫酸作用下,通过酯化反应制得乙酸丁酯,反应温度为115~l25℃,反应装置如图.下列对该实验的描述错误的是( )