“How long have you been playing the violin?” Which word is the noun in the sentence above?

My uncle has more than a hundred ____ on his farm.

Our living room has some _______. There are two armchairs, a sofa, and a coffee table.

What is an uncountable noun?

Please throw away your trash in the bin. From the sentence above, ____ is an uncountable noun.

I am going to visit my uncle next week. You can see fish swimming in the river for the water __ crystalline there.