**Core Concept**
Respiratory distress syndrome (RDS) in newborns is primarily caused by a deficiency of surfactant, a complex substance produced by type II pneumocytes in the lungs. Surfactant reduces surface tension in the alveoli, facilitating lung expansion during inhalation and preventing alveolar collapse during exhalation.

**Why the Correct Answer is Right**
Surfactant is rich in a specific type of lipid called phospholipids, particularly phosphatidylcholine (lecithin). The absence or insufficiency of surfactant leads to increased surface tension in the alveoli, causing them to collapse and leading to respiratory distress. The increased pCO2 in the arterial blood gas analysis is a consequence of hypoventilation due to the impaired lung function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not mention any specific lipid associated with surfactant. While it might sound plausible, it lacks specificity.
**Option B:** This option is incorrect because it does not specify the type of lipid associated with surfactant. Although it is a general category of lipids, it is not the correct answer.
**Option C:** This option is incorrect because it is a type of lipid, but it is not the primary component of surfactant in the context of RDS.

**Clinical Pearl / High-Yield Fact**
A simple mnemonic to remember the primary component of surfactant is "PC" which stands for Phosphatidylcholine (lecithin), the key lipid responsible for reducing surface tension in the alveoli.

**Correct Answer: C. Phosphatidylcholine**