下列关于二氧化碳的叙述中,错误的是[ ]
A.自然界中二氧化碳处于循环状态
B.二氧化碳可用于生产碳酸饮料
C.干冰可用于储藏食物和人工降雨
D.可用氢氧化钠溶液检验二氧化碳
答案:D
The students were very tired. They stopped _____ a rest.[ ]
A. to have
B. have
C. having
D. has
简述饭店成本控制的重要性