Here are the rewritten versions of your original content:
- They underestimated his ability when they promoted him.
- Experiment is a countable noun in English.
- His outstanding ability earned him a place on the team.
They underestimated his ability when they promoted him.
他们提拔他的`时候高估了他的能力。
Contestants were grouped according to age and ability.
参赛者按年龄和能力分组.
