Definition: used to refer to a particular person or thing in a group Level: A2
他是唯一一个能解决这个问题的人。
He is the ___one who can solve this problem.
我手机的一个缺点是电池续航时间短。
___One drawback of my phone is its short battery life.
我的一个表亲下周要来看我。
___One of my cousins is coming to visit next week.
