His fingerprints were the [ a dead ] giveaway.是什么意思？

His fingerprints were the [ a dead ] giveaway.

他的指纹成为暴露他真面目的关键.

his

pron. (he的所有格)他的，(he的物主代词)他的东西；det. 属于他的，用于名词前，自己的，指某人的，上帝的；

例句
He claimed that his parents had abandoned him...
他声称父母遗弃了他。

fingerprints

n. 指纹( fingerprint的名词复数 )；v. 指纹( fingerprint的第三人称单数 )；

例句
His fingerprints were on file in Washington...
他的指纹已在华盛顿记录在档。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

dead

adj. 死去的，完全的，无感觉的，呆板的；adv. 完全地，非常，绝对，极度；n. 死者，（死一样的）寂静，极寒时候；

例句
According to police accounts, Mr and Mrs Hunt were found dead on the floor of their kitchen.
据警方称，亨特夫妇被发现死在家里厨房的地板上。

giveaway

n. 泄漏，免费样品，赠品，（电台中的）有奖问答节目；

例句
The only giveaway was the look of amusement in her eyes.
唯独她俏皮的眼神使事情露馅儿了。