250.But those captured were anything but terrorists, most of them illegal immigrants from Central or South America.

英语四级译文:
被逮捕的并非恐怖主义者，其中大多数是来自中美与南美的非法移民。

四级词汇讲解:
本句的主干是those were anything but terrorists。过去分词captured为代词those的后置定语，两者为被动关系;most of them illegal immigrants from Central or South America对主语those起到了补充说明的作用，其中them指代的就是those，这句还可以替换为非限制性定语从句: most of whom were illegal immigrants from Central or South America。

anything but的意思是“决不，根本不”，属于肯定形式表达否定含义的情况。如:
The bridge is anything but safe.这桥一点也不安全。

英语四级考点归纳:
其他肯定形式表达否定含义的短语还有:

※ far from意为“远非...，完全不”。如:
His plan is far from satisfactory.他的计划完全无法令人满意。

※ the last+名词+to不定式/从句，意为“最不……”。如:
That is the last thing to happen.那是最不可能发生的事。

※ fail to意为“无法”。如:
We failed to negotiate with them.我们无法与他们协商。

※ be free from意为“没有，不”。如:
I was free from work last week.我上个星期没有上班。

※ let alone意为“更别说，更谈不上”。如:
I never know him, let along his family.我从不认识他，更别提他的家人了。

※ in vain意为“徒劳，无法办到”。如:
She tried to find out the truth, but in vain.她试图找出真相，但没做到。