Here is the item again:
Anyone who visits Neil will find uneaten fruit all over his
apartment. (A)
Such as rotting bananas on the kitchen counter,
(B) desiccated grapes
in a bowl on the coffee table, (C)
and a drippy apple on the bureau by the bed.
You correctly realized that the period after apartment creates a fragment. Such as rotting bananas ... is an afterthought phrase, so it cannot stand alone as a complete sentence.
To fix this fragment, you chose to do this:
Anyone who visits Neil will find uneaten fruit all over his
apartment. For instance, he has rotting
bananas on the kitchen counter, desiccated grapes in a bowl on the coffee
table, and a drippy apple on the bureau by the bed.
By adding a subject, he, and a verb, has, you have given the fragment the main clause that it needs to be a complete sentence.
Let those right answers ring out!