询问价格：How much is it? — 英语选择题
题目
Tom在商店购物。店员告诉他：'The ruler is six yuan. The ruler and the schoolbag are twenty yuan in all.' Tom想买schoolbag，他问：'How much is the schoolbag?' 店员应该回答：
A. It's six yuan.
B. It's fourteen yuan.
C. It's twenty yuan.
D. It's twenty-six yuan.