a is
How much is this belt?
How much does this belt cost?还是不太懂，看书上有How much is this belt?的原句，知道是选A。How much is this belt cost？和 How much does this belt cost? 两种用法有啥不同？is 不能陪合 动词原形使用的。用How much is this belt？本省就完整的句子了，后面那个动词COST加上去多余。如果COST做名词的话还是可以的。看仔细了：How much is this belt's cost?这条皮带的成本是多少？“How much is this belt cost？和 How much does this belt cost?” 这样说对吗？这两种用法有啥不同？How much is this belt cost? 是有语法错误的。原因解释过了。How much is this belt's cost? 这条皮带的成本是多少？How much is this belt? = How much does this belt cost? 这条皮带多少钱？