They were totally mystified by the girl's disappearance.是什么意思？

They were totally mystified by the girl's disappearance.

那女孩失踪使他们大惑不解。

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

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。

totally

adv. 完全，整个地，全部地，百分之百，干净；

例句
Their relationship was totally asexual.
他们之间的关系根本与性无关。

mystified

v. 使（某人）困惑不解，使迷惑( mystify的过去式和过去分词 )；

例句
The audience must have been totally mystified by the plot...
观众一定是让剧情完全搞晕了。

by

prep. 在…旁边，表示方式，由于，经过；adv. 经过，表示保留或保存时用，短暂拜访；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

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。

disappearance

n. 消失，不见，消散，失踪，出走，一去不返；

例句
She knows how your brother's disappearance weighs upon you.
她知道你哥哥的失踪让你有多忧虑。