Countable nouns refer to things that can be counted, and have a singular and plural form, like apple/apples. Uncountable nouns refer to things that cannot be counted, they do not have a plural form, for example: rice, milk. From the given options, A is correct as 'alphabet' refers to a set of letters of a language. The plural of alphabet is alphabets and it's a countable noun. Option B is incorrect because the noun is not an uncountable, it can be modified by a number, hence it's countable. Option C is incorrect because the question asks for nouns to be picked out, and 'he' is a pronoun. Option D is incorrect because 'he' is not a noun, so it can't be countable or uncountable and 'alphabet' is a countable, and not an uncountable noun.