Assuming the bolded words are: <em>"for strong bones and teeth"</em> and that you had to choose between:
- <em>noun phrase</em>
- <em>adverb phrase</em>
- <em>verb phrase</em>
- <em>adjective phrase</em>
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.
A. It gives readers a sense of grasping for something that can't be caught.
