How is the production of mercury from burning coal an environmental hazard?

What does all of the organ system in a human form

What is the difference between bacterial infections and viral infections?

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