Final answer:
The first step in root canal therapy is the administration of local anesthesia.
Step-by-step explanation:
The correct answer is 4) Administration of local anesthesia
In root canal therapy, the first step is the administration of local anesthesia. This is done to numb the area around the tooth and prevent pain during the procedure. After the anesthesia is given, the dentist will proceed with cleaning and shaping the root canal, followed by obturation of the root canal, and finally the placement of a temporary filling, if necessary.