The discussion came (alive) when an interesting topic was brought in.

alive是形容词,come变得 所以说当一个有趣的话题出现时,议论就又活跃起来啦,也可形容课堂活跃,有生气啊,所以是对的
形容词 a.[F]
1.活着的;现存的[Z]
The injured man is unconscious but still alive.
受伤的人不省人事但仍活着.
2.有活力的,有生气的,活跃的
Although he is eighty,he is still very much alive.
他虽有八十岁了,但仍然充满了活力.
3.敏感的,注意到的[(+to)]
Are you alive to what is going on?
你注意到正在发生的事吗?
4.热闹的;充满的[(+with)]
The town was alive with rumors.
镇上谣言四起.
5.通着电流的
The wire is alive.
这条电线带电.