Unsaturated fatty acids are a type of fatty acid that contain one or more double bonds in their carbon chain. These double bonds create kinks in the carbon chain, which can prevent the molecules from packing closely together. This property of unsaturated fatty acids makes them liquid at room temperature and provides several health benefits.

The correct option that contains only unsaturated fatty acids is option C: Timnodonic acid, Linolenic acid, Linoleic acid. Let's understand each of these fatty acids in detail:

1. Timnodonic acid: Timnodonic acid, also known as eicosapentaenoic acid (EPA), is an omega-3 fatty acid. It is found in fatty fish such as salmon, mackerel, and sardines. EPA has been shown to have anti-inflammatory properties and is beneficial for heart health.

2. Linolenic acid: Linolenic acid is an omega-3 fatty acid that is essential for the body. It is found in plant-based sources such as flaxseeds, chia seeds, and walnuts. Linolenic acid is converted into other omega-3 fatty acids, such as EPA and DHA, in the body. It plays a crucial role in brain function and has anti-inflammatory effects.

3. Linoleic acid: Linoleic acid is an omega-6 fatty acid that is also essential for the body. It is found in vegetable oils such as sunflower oil, safflower oil, and corn oil. Linoleic acid is involved in the synthesis of other important molecules in the body, such as prostaglandins and leukotrienes.

These three fatty acids are all unsaturated and have important roles in the body. They are considered essential fatty acids because the body cannot produce them on its own and they need to be obtained from the diet.

In contrast, the other options contain saturated fatty acids:

- Option A (Palmitic acid, Myristic acid, Lauric acid): These are all saturated fatty acids commonly found in animal fats and tropical oils. They are solid at room temperature and have been associated with increased risk of cardiovascular diseases.

- Option B (Stearic acid, Arachidic acid, Arachidonic acid): Stearic acid and arachidic acid are saturated fatty acids, while arachidonic acid is a polyunsaturated fatty acid. Arachidonic acid is found in animal fats and is involved in inflammation and immune response.

Therefore, the correct option that contains only unsaturated fatty acids is option C: Timnodonic acid, Linolenic acid, Linoleic acid.