`IV.`
`1.` since `->` for
Giải thích:
+) since + mốc thời gian
+) for + quãng thời gian
`2.` to protecting `->` to protect
Giải thích: to V = so as to V: để làm gì
`V.`
`1.` All the students love the principal because of his kindness.
`2.` I'm sorry for having forgotten the tickets.
`3.` The house at the end of the street which has been empty for years has been sold.
@ `Ly`