N−3 fatty acids (popularly referred to as ù−3 fatty acids or omega-3 fatty acids) are essential unsaturated fatty acids with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain. The omega-3 fatty acids are "essential" fatty acids because they are vital for normal metabolism and cannot be synthesized by the human body. (Hence, statement 3 is correct.)
Omega-3 fatty acids are made by marine microalgae. These are then consumed by fish and accumulate to high levels in their internal organs. (Hence, statement 1 is correct.)
Some evidences suggest that people with certain circulatory problems, such as varicose veins, may benefit from their dietary consumption, which may stimulate blood circulation, increase the breakdown of fibrin, a compound involved in clot and scar formation, and may reduce blood pressure. Evidently, Omega-3 fatty acids reduce blood triglyceride levels and regular intake may reduce the risk of secondary and primary heart attack. (Hence, statement 2 is also correct.)