Eng

Challenging...

苦

Bitter, Challenging, Difficult, Hard, Miserable, Suffering

具挑戰性

Challenging

(Challenge, Challenged, Challenges, To challenge)

艱鉅

Arduous, Challenging, Difficult, Hard

艱苦

Arduous, Challenging, Difficult, Hard

棘手

Challenging, Difficult, Tricky

棘手的

Challenging, Difficult, Tricky

挑戰

Challenge, Challenged, Challenges, Challenging, To challenge

挑戰性

Challenging

(Challenge, Challenged, Challenges, To challenge)