how much 一般问物品的价格，how much 后面省略了money，即提问的
中心词是money，所以当提问价格时，既可以对单数或
不可数名词提问，又可以对复数名词提问。如果对单数或不可数名词提问，回答用It is +钱数，如果对复数名词提问，回答用They are + 钱数。
How much is this book?
It's ten yuan.
How much are the apples?
They are five yuan a kilo.
另外，对价格提问还可以这样问和回答：
How much did you spend on your bike?
I spent 300 yuan on my bike.
How much does the watch cost?
It costs 200 yuan.
How much is the necklace worth？
It worth 1000 yuan.
how much除了问物品的价格外，还可以对不可数名词提问，回答时用具体的量词，如：
How much water do you have?
I have half bottle of water.
How much water is there left?
There is only a little water left.
祝你学习进步，更上一层楼！愿我们互相帮助，共同进步！请记得采纳，谢谢~O(∩_∩)O~