Did dinosaurs and humans exist at the same time?

Some birds look for food near cattle and other livestock. the movement of the cattle churns up the ground, making insects available to the birds. the cattle appear to be unaffected by the presence of the birds. what kind of relationship exists between the birds and the cattle? o a. parasitism o b. commensalism o c. predation o d. mutualism

How can an organ, such as the lungs, work for multiple body systems?

Crossing over is a method of (blank)?