Final answer:
In the event of a collision resulting in injury, the first action should be to call for emergency medical assistance to ensure the injured party receives immediate care.
Step-by-step explanation:
If you have been involved in a collision that resulted in the other driver being injured, the first thing you should do is: C) Call for emergency medical assistance. This is because ensuring the safety and attending to the health needs of the injured party is the most critical action. You should not attempt to move the injured person unless there is an immediate threat to their safety, such as a fire, as moving someone without proper training could exacerbate their injuries. After securing medical help, you can proceed to exchange insurance information and follow any other required post-accident procedures. Remember that leaving the scene immediately would be both unethical and, in many places, illegal.