What do you usually do on Thanksgiving Day?

1. I visit my grandparents'.
2. I visit my grandparents' house.
3. I visit my grandparents' home.
4. I visit my grandparents' apartment.
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Which one is omitted after "grandparents'"?

All of them could work. Either a house or an apartment is considered someone's home.

Home

The correct answer is "house" because "house," "home," and "apartment" are all specific places where someone can visit. In this case, the word "house" gives more information about the location where you visit your grandparents. "Grandparents'" alone simply indicates that you are visiting your grandparents, but it does not specify where.