Countable nouns name things or beings that can be counted. For example, one apple, three bears, etc.
Uncountable nouns cannot be counted, because they refer to quantity or mass. For example, some milk, some apple juice, etc.
Option A: 'Amount' refers to the quantity of something. It cannot be counted, and is hence uncountable. So, option A is right.
Options B and D: The noun 'amount' refers to a quantity and hence cannot be counted. It indicates a mass and hence is an uncountable noun.
Options C and D: 'Much' is a quantifier and indicates the amount or degree of something. It means 'a large amount'. It's not a noun and hence cannot be categorized as countable or uncountable.
Hence options B, C and D are incorrect.