**Core Concept**
The question tests the ability to differentiate between various causes of pneumonia in a non-smoker, highlighting the importance of radiographic evidence in diagnosis. **Community-acquired pneumonia (CAP)** is a common condition, and its causes can be diverse, including viral, bacterial, and atypical pathogens.

**Why the Correct Answer is Right**
The correct answer is likely **Pneumocystis jirovecii pneumonia (PCP)**, a type of opportunistic infection that predominantly affects immunocompromised individuals. PCP is caused by the fungus Pneumocystis jirovecii, which can lead to diffuse bilateral interstitial infiltrates on chest radiographs. Non-smokers with compromised immune systems, such as those with HIV/AIDS, are at an increased risk of developing PCP. The symptoms of PCP can include flu-like symptoms, such as fever, cough, and shortness of breath, followed by radiographic evidence of consolidation in the lungs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but it could be a distractor for other causes of pneumonia in non-smokers, such as Staphylococcus aureus or Klebsiella pneumoniae. These bacteria can cause pneumonia in non-smokers, but they are less likely to present with diffuse bilateral interstitial infiltrates on chest radiographs.
* **Option B:** This option could be a distractor for viral pneumonia, such as respiratory syncytial virus (RSV) or influenza. Viral pneumonia can present with flu-like symptoms, but it is less likely to cause consolidation in the lungs.
* **Option C:** This option could be a distractor for Mycoplasma pneumoniae, which is a common cause of CAP in young adults. However, Mycoplasma pneumoniae typically presents with lobar consolidation rather than diffuse bilateral interstitial infiltrates.

**Clinical Pearl / High-Yield Fact**
PCP is a classic cause of pneumonia in immunocompromised patients, and its diagnosis requires a high index of suspicion. When evaluating a patient with flu-like symptoms and radiographic evidence of consolidation in the lungs, consider PCP in the differential diagnosis, especially if the patient has a history of immunosuppression.

**Correct Answer:** C. Pneumocystis jirovecii pneumonia (PCP).