Final answer:
The appropriate time to actively rewarm frostbite is after consulting medical direction.
Step-by-step explanation:
The appropriate time to actively rewarm frostbite in the field is c) After consulting medical direction. It is crucial to consult medical direction before attempting to rewarm frostbite as improper rewarming can cause more harm. Medical professionals will provide specific instructions and guidance on how to safely rewarm frostbite based on the severity and location of the frostbite.