The landslides happened. Many people were sleeping at this time. A. Before the landslides happened, many people were sleeping.

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The landslides happened. Many people were sleeping at this time.

Before the landslides happened, many people were sleeping.

While the landslides happened, many people were sleeping.

After the landslides happened, many people were sleeping.

When the landslides happened, many people were sleeping.

Giải thích

Đáp án đúng: D

Giải thích: Câu diễn tả một hành động đang xảy ra (thì quá khứ tiếp diễn) thì hành động khác xen vào (thì quá khứ đơn): When S + V2, S + was/were + V-ing…

Dịch nghĩa: Khi các vụ sạt lở xảy ra, nhiều người đang ngủ.