The correct option is (a).
Explanation
Water and cooking oil are both liquids at room temperature, yet they exhibit fundamentally different physical and chemical properties, particularly regarding their composition and reaction to heat.Statement 1 is Correct: Water and cooking oil differ in odour and inflammability. Pure water is generally odourless, whereas cooking oils possess distinct odours depending on their source. Furthermore, cooking oil is inflammable (combustible), while water is non-combustible.
Statement 2 is Incorrect: While water is used to extinguish fires, the assertion that oil does not burn in air is false. Cooking oil is a fuel; it burns in air when heated to its ignition temperature. Oil fires are dangerous because oil acts as the combustible material.
Statement 3 is Incorrect: Water and oil are not chemically the same. Water ($H_2O$) is a simple inorganic molecule. Cooking oils are complex organic compounds, typically triglycerides (esters of glycerol and fatty acids) containing long chains of carbon and hydrogen. Thus, they differ both chemically and physically.
Key Takeaway: The primary distinction between water and cooking oil lies in their chemical composition (inorganic vs. organic) and their reaction to fire (non-combustible vs. combustible).