The wild geese are generally arranged in a neat herringbone or flanking flight, which is a manifestation of the instinct of the cluster. Because this is conducive to defending against the enemy. The geese are always experienced old geese as "captains" and fly in the front of the team. In flight, the geese leading the team are exhausted, so they often exchange positions with other geese. Baby birds and frail birds are always inserted in the middle of the team. Therefore, they will not be subject to enemy forces during flight. Harmful attack. Which of the following, if true, can be a prerequisite for reaching the above conclusions? ['The flight formation of A Dayan has both defense and attack functions.', 'Weakness cannot be a team leader.', 'Enemies will not attack the middle of the geese flight queue while flying.', 'There must be more than one wild goose in the flock.']