https://online2.tingclass.net/lesson/shi0529/0001/1240/19-04.mp3
https://image.tingclass.net/statics/js/2012
23. We have taken all the ____ we can against the painting being stolen.
A. precautions B. admissions C. concessions D. transactions
<precaution>
precaution 预防措施，警惕
caution 警告
</precaution>
