Suppose I want to teach a non-English speaker the word fruit. If I'm referring to a container full of different fruit, can I ask a question like this? "What are those?" and answer " They are fruit".

Should the word fruit be considered uncountable or countable?

If we consider the word fruit to be uncountable, Is the form of this question and answer correct?

or it's better to say it like this "What's that?"and the answer is "It's a fruit plate."