Viết các câu sau ở thể khẳng định (+), thể phủ định (-), thể nghi vấn (?) ở thì hiện tại hoàn thành.

`1` `:` `(+)` I have finished my homework

`→` `(-)` I haven't finished my homework

`→` `(?)` Have I finished my homework `?`

`-----------`

`2` `(-)` My uncle hasn't been to Singapore before `.`

`→` `(+)` My uncle has been to Singapore before `.`

`→` `(?)` Has my uncle been to Singapore before `?` 

`----------`

`3` `(?)` They have found their keys `?`

`→` `(-)` They haven't found their keys

`→` `(+)` They have found their keys 

`----------`

`4` `(+)` Jim has just played video games with his brother

`→` `(-)` Jim hasn't just played video games with his brother

`→` `(?)` Has Jim just played video games with his brother `?` 

`----------`

`@` Thì HTHT `:`

`@` Dấu hiêu nhận biết `:` just , before , already , never , ever , Since + mốc tg , For + khoảng tg

`@` Form `:`

`+` S `(` số ít `)` `+` has `+` Ved/3

`+` S `(` số nhiều `)` `+` have `+` Ved/3

`-` S `(` số ít `)` `+` hasn't `+` Ved/3

`-` S `(` số nhiều `)` `+` haven't `+` Ved/3

`?` Has `+` S `(` số ít `)` `+` Ved/3

`?` Have `+` S `(` số nhiều `)` `+` Ved/3