1. There is a banana and an apple on the floor." 2.There are a banana and an apple on the floor." 3"There are bananas and an apple on the floor."
4"There is a banana and apples on the floor."

I am confused with the rules of using "is" and "are". Please tell me which one is correct and which one is not.

1 and 3 are right

Explanation:

"is" is used for singular things

"are" is used for multiple things

So "are bananas" is correct, but "are banana" wouldn't be

"There is a banana and an apple on the floor."

Explanation:

If the sentence was talking about MULTIPLE apples and bananas, then you would use "are".

"There are bananas and apples on the floor." This would be the correct way of writing it if there were multiple bananas and apples in the sentence. (Which also means taking the word "an" out of the sentence, this is because we aren't taking about two/multiple singular nouns anymore.)

The word "is" is correctly used when talking about singular nouns, example "banana" and "apple". Since we didn't add an s to make it multiple apples/bananas we would use the word "is" because we are talking about singular nouns.

I hope this helped, if there is anything you want me to explain more thoroughly don't be afraid to say so. I'm happy to help!