Challenging

苦

Bitter, Challenging, Difficult, Hard, Miserable, Suffering

挑戰

A, Challenge, Challenged, Challenges, Challenging, The, To

棘手

Challenging, Difficult, Tricky

艱苦

Arduous, Challenging, Difficult, Hard

艱鉅

Arduous, Challenging, Difficult, Hard

具挑戰性

Challenging

挑戰性

Challenging

棘手的

Challenging, Difficult, Tricky