There were at least three _____________ - grandparents, parents, children - at the party.

There were at least three __generations___________ - grandparents, parents, children - at the party.

_______________________________

vì:

Đằng sau là grandparents, parents, children `->`  người thuộc 3 dòng họ

`->` dùng generation

`->` vì là số nhiều nên chọn "generations"

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