s. stimulating interest or thought
s. disturbingly provocative
a. 挑战的, 引起争论的
1. This math problem is very challenging for me.
这个数学题对我来说非常具有挑战性。
2. She enjoys taking on challenging projects at work.
她喜欢在工作中接受具有挑战性的项目。
3. Climbing a mountain can be a challenging but rewarding experience.
爬山可能是一个具有挑战性但又有回报的经历。