What structure is more complex is a tissue or an organ

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

Which would be the most useful source of evidence to support mcneill's contention?

What is the average speed of a car that traveled 300.0 miles in 5.5 hours