## Core Concept
The question tests knowledge of the fatty acid composition of various cooking oils, specifically focusing on the content of polyunsaturated fatty acids (PUFAs). PUFAs are a type of unsaturated fat that are essential for human health, playing critical roles in inflammation, brain function, and the structure of cell membranes.

## Why the Correct Answer is Right
Among common cooking oils, **Sunflower oil** is known for its high content of polyunsaturated fatty acids. It predominantly contains linoleic acid, an omega-6 fatty acid, which is a type of PUFA. This high PUFA content makes sunflower oil a good option for individuals looking to increase their intake of unsaturated fats.

## Why Each Wrong Option is Incorrect
- **Option A:** While **Mustard oil** does contain a mix of monounsaturated and polyunsaturated fats, its PUFA content is not as high as that of sunflower oil. It is rich in alpha-linolenic acid (an omega-3 fatty acid) and oleic acid (a monounsaturated fatty acid).
- **Option B:** **Groundnut (Peanut) oil** has a balanced mix of monounsaturated and polyunsaturated fats but tends to have a lower PUFA content compared to sunflower oil. It is predominantly composed of oleic acid, a monounsaturated fatty acid.
- **Option C:** This option might seem plausible but given the choices and typical compositions, it's less likely to be correct without specific details on the oil.

## Clinical Pearl / High-Yield Fact
A key point to remember is that while PUFAs are essential, a balanced intake of omega-6 and omega-3 fatty acids is crucial for health. Excessive intake of omega-6 fatty acids, without a corresponding increase in omega-3 fatty acids, can potentially lead to an increased risk of inflammation.

## Correct Answer: C. Sunflower oil