The correct answer is A. a gift from my grandfather
Step-by-step explanation:
A nonessential appositive phrase refers to a set of words that are not necessary for the main sentence but provide extra information or explain one of the essential elements. They can be identified because they are commonly enclosed by commas that show they are not essential to the sentence. This means, in the sentence presented "a gift from my grandfather" is the nonessential appositive phrase because this phrase explains the element "our telescope" but it is not essential to understand the main sentence "Our family enjoys stargazing with our telescope when we go camping" and it is enclosed by commas as all appositive phrases of this kind.