"He is my close friend."
Translation:C'est mon ami intime.
This is a rule you will have to apply VERY often on Duolingo. In French, "c'est" (sing.) and "ce sont" (plural) are used in a large variety of expressions, when a pronoun (it, she, he, they) is subject of verb "être" and followed by a nominal group, ie: article (+ adjective) + noun. - it is + noun => c'est - she is + noun => c'est - he is + noun => c'est - they are + noun => ce sont