Countable nouns refer to things that can be counted, they have a singular and plural form, like apple/apples. Uncountable nouns are nouns that cannot be counted, and they do not have a plural form, like rice, flour, milk. In option A, 'officer' refers to a person, persons can be counted, and 'cup' can also be counted, hence they're countable nouns. Water cannot be counted, you can't say three waters or few waters, hence it's an uncountable noun and option A is thus, correct. Option B is incorrect, as 'officer' and 'cup' are not uncountable, they have a plural form officers and cups, and water cannot be counted, hence it's not a countable noun. Option C is incorrect, officer and water have been correctly identified as countable and uncountable but cup is not an uncountable noun. It's a thing that has a plural form and can be counted as two cups, three cups and so on, hence it's a countable noun. In option D, the nouns are correctly identified as countable and uncountable, but we've been asked to pick out all the nouns, 'officer' being a noun is missing from this option, hence option D is incorrect.