晚上独自开车可能很危险，所以总是要采取预防措施。

Driving alone at night can be dangerous, so always take ___precautions.

他们叫了医生作为预防措施。

They called the doctor as a ___precaution.

他采取了锁门的预防措施。

He took the ___precaution of locking the door.