If the operation ________ carefully prepared, it would not have been successful.
C
语法题：虚拟语气。
Itisimportantto________yourskinfromtheharmfulstrongsunlight.
Theypreferto_______therestofthemorningwalkinginthegarden.
Studentsshould_____theirowninterestsaswellasdotheirschoolwork.
When you're_____ a crisis, it often helps to talk to someone.