Calcium is essential for strong bones and teeth. what kind of phrase is the bolded words?

Assuming the bolded words are: "for strong bones and teeth" and that you had to choose between:

It is an adjective phrase (4).

An adjective phrase is a group of words complementing, specifying, or modifying a 'head' adjective in the sentence. It is called an adjective (or adjectival) phrase because the whole group of words functions as an adjective, which means it provides information about a noun.

Here, the adjective phrase "for strong bones and teeth" is specifying the head adjective "essential." It is functioning as an adjective for the noun "calcium" by giving us information about it.

no its not a run on sentence however i think you meant wet suits not sours also a run on sentence would be like surfers surf all winter long in southern california by using wet sours to keep them warm and the live their all year long