40
(A)untimely
(B)currently
(C)previously
(D)spontaneously

However, the U.S. Department of Homeland Security does currently use the technology for checking employees into some areas and for travelers enrolled in its PreCheck program.

但是，美國國土安全部目前使用該技術檢查員工進入某些地區以及參加PreCheck計劃的旅行者。

untimely 過早(可當形容詞或副詞)

previously 先前(副詞)

spontaneously 不由自主地(副詞)

D 自發地 ADV

求最後2句翻譯

 European airports have been much quicker to embrace the biometric technology than American airports. However, the U.S. Department of Homeland Security does 40 use the technology for checking employees into some areas and for travelers enrolled in its PreCheck program.