The sentence <em>My favorite memory is the time I went to visit my grandparents during summer vacation</em> would be in the introduction of an essay.
Explanation:
An effective <u>essay</u> is made up of three major parts: the introduction, the body and the conclusion. The first section aims to present the topic to the reader, give a hint of what the reader is going to find out and the overarching point, if there is a thesis statement. Then, the sentence <em>My favorite memory is the time I went to visit my grandparents during summer vacation </em>-as it serves to these ends-<em> </em>would be part of the introduction of a <u>narrative essay</u>, that is the one that tells a story.