**Core Concept**
The patient likely has a peritonsillar abscess (PTA), a severe complication of tonsillitis characterized by the collection of pus between the tonsillar capsule and the surrounding muscles. PTA requires prompt treatment to alleviate airway obstruction and prevent further complications.

**Why the Correct Answer is Right**
The initial therapy for PTA involves incision and drainage of the abscess, usually performed under general anesthesia. This procedure helps to alleviate airway obstruction, reduce pain, and prevent further complications. The patient's symptoms, such as difficulty swallowing and poor handling of secretions, are classic signs of a PTA. The fluctuant bulge in the posterior wall of the pharynx is consistent with an abscess.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibiotics alone may not be sufficient to treat a PTA, as the abscess requires drainage to resolve. Antibiotics can be used in conjunction with drainage to treat any underlying bacterial infection.
**Option B:** A tonsillectomy may be necessary in some cases, but it is not the initial therapy for PTA. Tonsillectomy is often considered after the abscess has been drained and the patient's condition has stabilized.
**Option C:** A soft tissue radiograph of the neck may show the abscess, but it is not the initial therapy. The radiograph is used to confirm the diagnosis and guide drainage.

**Clinical Pearl / High-Yield Fact**
PTA is a medical emergency that requires prompt treatment to prevent airway obstruction and further complications. The patient's symptoms, such as difficulty swallowing and poor handling of secretions, are classic signs of a PTA.

**Correct Answer:** C. Incision and drainage of the abscess.