challenge既是名词也是动词；所以名词形式还是challenge

challenge

n.挑战;艰巨任务;挑战书，提议;质询;质疑;提出异议

v.对…怀疑(或质疑);拒绝接受;向(某人)挑战;

现在分词： challenging

过去式： challenged

过去分词： challenged

chools must meet the challenge of new technology.

学校必须迎接新技术的挑战。

The company faces major challenges over the course of the next few years.

这家公司今后几年将面临重大的挑战。

It was a direct challenge to the president's authority.

这是对主席权威的直接质疑。

We need to challenge some of the basic assumptions of Western philosophy.

我们有必要向西方哲学的某些基本假设提出质疑。