题干
Guangzhou, Shanghai and other big cities are exciting places ______.
A：work
B：working
C：work in
D：to work in
答案(点此获取答案解析）
D
Guangzhou, Shanghai and other big cities are exciting places ______.
A：work
B：working
C：work in
D：to work in
通气，溶液中有气泡产生；中期可以闻到酒香；后期接种醋酸菌，适当升高温度并通气，酒香逐渐变成醋香。图乙中能表示整个发酵过程培养液pH变化的曲线是