hard

Diamond is the hardest natural substance known on Earth.

(Chinese) 钻石是地球上已知的最坚硬的自然物质。

The ground was too hard for the gardener to dig a hole for the tree.

(Chinese) 土地太硬了，园丁没法给树挖坑。

The physics exam was so hard that only five students passed.

(Chinese) 物理考试太难了，只有五个学生及格。

It is hard for him to wake up early on cold winter mornings.

(Chinese) 在寒冷的冬日早晨，他很难早起。

She studied hard all night to prepare for her medical boards.

(Chinese) 她整晚努力学习，为医学执照考试做准备。

He hit the ball so hard that it flew over the stadium fence.

(Chinese) 他球打得非常用力，球飞过了体育场的围栏。