`1.` While sorting the donations, he realized how generous people were.

`+)` While + S + V

`2.` I haven't updated this smartphone for `2` months.

`+)` for + khoảng thời gian

`+)` HTHT: S + have/has + not + V-ed/P2 + O

`3.` The internet allows us to communicate over long distances.

`+)` HTĐ: S + V-s/es + O

`+)` allow sb to do sth: cho phép ai đó làm điều gì đó

`4.` When we were having lunch, there was a knock at the door.

`+)` hành động đang xảy ra thì hành động khác chen vào `->` QKTD

`+)` QKTD: S + was/were + V-ing + O

`+)` QKĐ: S + V-ed/V2 + O

`5.` Planting trees along the roads helps our environment.

`+)` HTĐ: S + V-s/es + O

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`@yt2704`