他的下落不明。

___His ___whereabouts are unknown.

然而，他的下落已经未知六年了。

However, ___his ___whereabouts have been unknown for 6 years.

尽管进行了广泛搜索，她的下落仍然难以捉摸。

Despite extensive searches, ___her ___whereabouts remain elusive.