你在信中提到你是Facebook的活跃用户。

You mention that you're already active on Facebook.

youdao

李：是的，你在信中提到了。现在你方有什么具体建议呢？

Yes. You have mentioned it in your letters. Do you now have anything specific?

youdao

你在信中提到弗兰克·威尔斯(Frank Wells)。他1994年在直升机失事中不幸身亡。

You mentioned in your letter Frank Wells, who died in a helicopter crash in 1994.

youdao