Carrier pigeons have a strong flying ability, reaching speeds of up to 100 kilometers per hour, and memory and recognition are outstanding among animals. It is not afraid of fatigue, loyal and reliable, has no deserters and surrenders, is not restricted by terrain, and delivers information in a timely manner. Since then, he has repeatedly made great achievements. What kind of opinion does this passage support? ['Carrier pigeons have strong flying ability.', 'Carrier pigeon is an animal suitable for combat activities.', 'Many unique advantages of carrier pigeons have great military effects.', 'The participation of pigeons in military activities is a guarantee of victory.']