Раскрой скобки ,употребив прилагательное в правильной форме.My sister is the [good]

Раскрой скобки ,употребив прилагательное в правильной форме.

My sister is the [good] pupil in her class.
It is a very [funny] English book.
In the city rivers are [dirty] than in the country.
Tigers are [big] than dogs.
Nick is the [bad] pupil in our class.
I thing dolphins are the [beautiful] animals.
Winter is a [cold] season.I like it.