adj.
困难的( hard的最高级 )；硬的；有力的；努力的
用作形容词(adj.)
The thirtieth math question was the hardest.
第三十道数学题是最难的。
The hardest thing is writing a recommendation for someone we know.
最难的事情，是为一个认识的人写介绍信。
权威例句
The hardest known oxide
The Hardest Context-Free Language.
Discovery of hardest known oxide
The hardest constraint problems: a double phase transition
