When people swim in the ocean, the body releases an invisible electrical signal. Researchers have developed a marine invisibility garment based on this situation. The invisibility clothing shields electrical signals released by the body, making it impossible for marine life such as sharks to detect People's tracks so that people can get up close and observe marine life such as sharks. Which of the following is a prerequisite for scientific researchers' assumptions? ['Some marine organisms use ultrasound to exchange information, forage, and find and avoid natural enemies.', 'Some fish have many cone cells in their retina, which can sensitively sense the subtle light changes in the water.', "Marine life such as sharks uses people's electrical signals to discover people's tracks.", "The invisibility garment is very thin and light, and will not hinder people's underwater activities."]