challengable:表示能力，有挑战力的；
challenging:表示属性，有挑战性的。
challenge
n.挑战；质疑；质询；挑战书
v.考查；盘问；对…怀疑（或质疑）；拒绝接受
复数：challenges 过去分词：challenged 现在分词：challenging
搭配
同义词
v.+n.
meet challenge,face challenge,accept challenge,pose challenge,present challenge
adj.+n.
big challenge,real challenge,great challenge,serious challenge,immediate challenge
n.
1.
挑战；艰巨任务a new or difficult task that tests sb's ability and skill
2.
挑战书；（比赛、打斗等的）邀请，提议an invitation or a suggestion to sb that they should enter a competition, fight, etc.
3.
~ (to sth)
质询；质疑；提出异议a statement or an action that shows that sb refuses to accept sth and questions whether it is right, legal, etc.