Hi !!
The verb "have" in present tense is has at the 3rd person singular
as all the verbs in present ; they all end with an "s" at the 3rd pers. singular.
"had" is the preterit (past simple) of "have"
so "have" is the infinitive
present = I, you, we, they have, or 3rd pers. sing => he/she/it has
past simple = had for all persons
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