**Core Concept**
The patient's symptoms are indicative of an allergic reaction, specifically anaphylaxis, triggered by the intake of an NSAID tablet. Anaphylaxis is a severe, life-threatening allergic reaction that can cause respiratory distress, skin manifestations, and cardiovascular instability.

**Why the Correct Answer is Right**
The patient's symptoms, including difficulty in breathing (dyspnea), appearance of bee hives (urticaria), rapid pulse rate (tachycardia), and low blood pressure (hypotension), are consistent with anaphylaxis. The mechanism of anaphylaxis involves the release of histamine and other mediators from mast cells, leading to increased vascular permeability, smooth muscle contraction, and respiratory and cardiovascular compromise. In this case, the NSAID tablet is likely the culprit, as it can trigger an allergic reaction in susceptible individuals.

**Why Each Wrong Option is Incorrect**
* **Option A:** Angina pectoris is a condition characterized by chest pain or discomfort due to myocardial ischemia, which is not consistent with the patient's symptoms of anaphylaxis.
* **Option B:** Hypertension is a condition characterized by high blood pressure, which is not consistent with the patient's low blood pressure (hypotension).
* **Option C:** Gastrointestinal bleeding is a condition characterized by bleeding from the gastrointestinal tract, which is not consistent with the patient's symptoms of anaphylaxis.

**Clinical Pearl / High-Yield Fact**
Anaphylaxis is a medical emergency that requires immediate treatment with epinephrine, antihistamines, and corticosteroids. Patients with a history of anaphylaxis should carry an EpiPen or other epinephrine injector with them at all times.

**Correct Answer:** C. Anaphylaxis.