Birth defects may be caused by a variety of environmental agents, called , which include some bacteria and viruses, various drugs and chemicals, and radiation.

a and c are the answeres

what is this saying?

here is the answer

water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.