Why used ”had” ?

had visited , which is a past participle ,
it indicates past or completed action or time

咁可能你會confused 點解唔用present perfect
present perfect (has visited) , which means 佢而家都仲有visit 個store
但你句句子, 雖然我唔知上文下理, 但係如果用had visited ,
which means 佢只係過去既幾個specific time 到visit過間store, 而家已經冇再去
所以就用had~.

睇你都係 copy 唔晒成句
但你可以見到 after 姐係佢 has visited(岩岩去完) 都過去左 所以要變成 had

而4樓果句真係精簡到爆 足夠晒解釋全部-.-!

過去既過去!!!!!!

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had visited=過去完成式，甚少單獨使用。是比過去式發生更早的時式。

文中應講述兩件已發生左既事，已had visited the store一定比另一件事發生得早。