Option 1 states that fish is a first-class protein because it contains essential amino acids. Amino acids are the building blocks of proteins, and there are two types: essential and non-essential. Essential amino acids cannot be produced by the human body and must be obtained through diet. Non-essential amino acids can be synthesized by the body.

Fish is considered a first-class protein because it contains all the essential amino acids that the body needs for proper growth, repair, and functioning. These essential amino acids are important for various bodily functions, including the synthesis of enzymes, hormones, and antibodies. Fish, being a good source of these essential amino acids, makes it a high-quality protein option in the diet.

Therefore, option 1 is correct, as it accurately describes the inclusion of essential amino acids in fish.