what is the simplest way to explain how to choose between HAVE and HAS in sentences
eg: I have got a car
she has got a car
"Has" is used in the third person singular (he, she, it) of the present tense. "Have" is for all other subjects in the present tense (I, you, we, you plural,they).
I hope that helps.
author of The Secret Lives of English Verbs