**Core Concept**
Type 2 Brittle Asthma is a severe and unpredictable form of asthma characterized by sudden, severe exacerbations and a marked variability in lung function. The pathophysiology involves a complex interplay of airway inflammation, bronchoconstriction, and airway remodeling.

**Why the Correct Answer is Right**
The drug of choice for treatment of Type 2 Brittle Asthma is **inhaled magnesium sulfate**. Magnesium sulfate has a rapid onset of action and can help to relax airway smooth muscle, leading to bronchodilation. It is particularly useful in acute settings where rapid control of symptoms is needed. The mechanism of action involves the inhibition of calcium influx into airway smooth muscle cells, which reduces the contraction of these cells and leads to bronchodilation.

**Why Each Wrong Option is Incorrect**
**Option A:** Other options such as systemic corticosteroids, bronchodilators, and leukotriene modifiers may be used in the management of brittle asthma but are not the primary choice for acute exacerbations.
**Option B:** Inhaled corticosteroids are a cornerstone of asthma management but are not effective in rapidly controlling acute exacerbations of brittle asthma.
**Option C:** Oxygen therapy is often used to treat hypoxemia in asthma exacerbations but does not address the underlying pathophysiology of brittle asthma.

**Clinical Pearl / High-Yield Fact**
Inhaled magnesium sulfate can be used as a rescue medication in acute asthma exacerbations, particularly in patients with Type 2 Brittle Asthma.

**Correct Answer:** A. Inhaled magnesium sulfate.