請教英文選擇問題~~?

你的懷疑是正確的。這題答案是(B)。

英語同一句中，過去完成式發生的時間比過去式早。既然這裡是 most of the quests had left，表示在他 got home 之「前」，客人已經離開了。所以（A）必須把 after 改成 before 才正確：

Before he got home, most of the guests had left.
= By the time he got home, most of the quests had left.

正解是(B)。

The "After" acts as a preposition which is together with "he got home" to form a prepositional clause and to modify the subject clause "most of the guests had left." In the case of "By the time he got home " should be changed to "By the time he get home." and the subject clause will be changed to "most of the guests are leaving sooner or later." Yip