自2010年至今的四级考试中， 共出现过 次
自2010年至今的六级考试中， 共出现过 次
N-COUNT 代理人;代理商 An agent is a person who looks after someone else's business affairs or does business on their behalf.
You are buying direct, rather than through an agent.
...a written declaration by someone, authorizing another person to act as his agent.
N-COUNT （艺术领域的）代理人，经纪人 An agent in the arts world is a person who gets work for an actor or musician, or who sells the work of a writer to publishers.
N-COUNT 间谍；特务 An agent is a person who works for a country's secret service.
All these years he's been an agent for the East.
N-COUNT 动力;媒介;因素;工具 If you refer to someone or something as the agent of a particular effect, you mean that they cause this effect.
In many societies young men regard themselves as highly active, the agents of change, shapers of the world.
N-COUNT （化学）剂;作用剂 A chemical that has a particular effect or is used for a particular purpose can be referred to as a particular kind of agent.
...the bleaching agent in white flour.
...fibrinogen, a blood clotting agent.