**Core Concept:** Linoleic acid is an essential fatty acid (EFA) that cannot be synthesized by humans and must be obtained from the diet. It is a polyunsaturated fatty acid (PUFA) with the chemical formula C18:2n-6.

**Why the Correct Answer is Right:** Linoleic acid is prevalent in various oils, but the one with the highest content is Sunflower Oil. Sunflower oil, extracted from the seeds of the sunflower plant, is rich in unsaturated fatty acids, particularly linoleic acid (C18:2n-6).

**Why Each Wrong Option is Incorrect:**

A. Soybean Oil: While soybean oil does contain linoleic acid, its percentage is lower than that of sunflower oil.

B. Olive Oil: Olive oil is rich in monounsaturated fatty acids, primarily oleic acid (C18:1n-9), and contains lesser amounts of linoleic acid.

C. Palm Oil: Palm oil is rich in saturated fatty acids and contains less linoleic acid compared to sunflower oil.

D. Groundnut Oil: Groundnut oil, also known as peanut oil, has a higher percentage of linoleic acid than olive oil but less than sunflower oil.

**Clinical Pearl:**

Sunflower oil is an essential component of a balanced diet due to its high content of linoleic acid, which plays a crucial role in maintaining cell membrane fluidity, regulating inflammation, and reducing LDL cholesterol levels. However, it should be consumed in moderation due to its high polyunsaturated fat content, which may increase the risk of omega-6 fatty acid-induced inflammation when consumed in excess.

**Correct Answer:** Sunflower Oil (C18:2n-6)