**Core Concept**
The patient's presentation of acute shortness of breath, hemoptysis, and a new systolic murmur in the context of a CXR suggestive of pulmonary hypertension and a history of smoking points towards a diagnosis of pulmonary embolism (PE) with possible associated pulmonary hypertension.

**Why the Correct Answer is Right**
The patient's symptoms and signs, including the new systolic murmur, suggest a possible association with pulmonary hypertension. The CXR shows evidence of pulmonary hypertension, with a prominent right heart border and a possible "snowman" sign. The ABGs show a slight increase in PCO2, suggesting some degree of right-to-left shunting. The patient's smoking history and BMI also increase the risk of PE.

**Why Each Wrong Option is Incorrect**
**Option A:** Pulmonary edema is less likely given the patient's ABGs and the absence of signs of left heart failure. While pulmonary edema can cause shortness of breath, it would typically be accompanied by more pronounced signs of fluid overload, such as orthopnea or paroxysmal nocturnal dyspnea.

**Option B:** While chronic obstructive pulmonary disease (COPD) can cause shortness of breath, the patient's CXR does not show the characteristic hyperinflation and emphysematous changes seen in COPD. Additionally, the patient's ABGs do not show the characteristic hypoxemia and hypercapnia seen in COPD.

**Option C:** Left ventricular strain on the EKG is a nonspecific finding that can be seen in a variety of conditions, including coronary artery disease, hypertension, and cardiomyopathy. However, the patient's presentation and CXR do not suggest a primary cardiac cause for her symptoms.

**Option D:** While the patient's BMI is elevated, the absence of other signs of sleep apnea, such as snoring or daytime somnolence, makes this diagnosis less likely.

**Clinical Pearl / High-Yield Fact**
Pulmonary embolism can be associated with pulmonary hypertension, which can be a life-threatening complication. The "snowman" sign on CXR, consisting of a dilated pulmonary artery and a prominent right heart border, is a classic radiographic finding in pulmonary hypertension.

**Correct Answer: B. Pulmonary embolism**