$39.$ The ladder is high for you to use it to hang Christmas decorations.

$*$ Cấu trúc : S + be + adj + for + smb + to + V_nguyên thể.

$40.$ She has learnt English since she was in grade 4.

$41.$ He has collected stamps since 2001.

$*$ Cấu trúc : S + have/has + V3 + for + khoảng thời giab/since + mốc thời gian.

$42.$ How long have you known that teacher ?

$*$ Cấu trúc : How long + have/has + S + V3 ?

$#Mei UwU$

`39`.This ladder is high enough for you to use it to hang Christmas decorations

`\rightarrow` Enough : S + be / be not + adj + enough ( for O ) + to V

`41`.She has learned English since she was in grade 4

`\rightarrow` Thì HTHT : S + have / has + V3 / PII

`\rightarrow` Đặc điểm nhận dạng : since

`44`.He has collected stamps since 2001

`\rightarrow` Thì HTHT : S + have / has + V3 / PII

`\rightarrow` Đặc điểm nhận dạng : since

`45`.How long have you first known that teacher ?

`\rightarrow` Thì HTHT ( CNV ) : Have / Has + S + V3 / PII ?

`\text{@ TheFox}`