If the subject of a sentence is two uncountable nouns, should the be verb and predicative be plural or singular? For example: water and soup______ ( be) _______ Are these two empty words singular or plural?

If the subject of a sentence is two uncountable nouns, should the be verb and predicative be plural or singular? For example: water and soup______ ( be) _______ Are these two empty words singular or plural?

Fill in are liquid
Water and soup are both liquid. It is obvious that the author is talking about two different things. Therefore, although water and soup are uncountable nouns, we should also use the plural here
Second: fill in liquid. You can understand it from two aspects. 1) liquid itself is an uncountable noun. It has no plural form, so it can only be used in the original form; 2) liquid can be used not only as a noun "liquid", but also as an adjective "liquid, liquid". So here you can also regard liquid as an adjective, and use it as a predicative after the verb be