do does ； cost costs的用法!
1：how much do the carrots cost?
the carrots cost three dollars.
2：how much does the tea cost?
the tea costs two euros.
3：how much does a movie ticket cost?
a movie ticket costs nine pounds.
问：为什么第一句用do,第二句用does呢?为什么第二句和第三句回答中不用cost,而是用costs呢?