When did the first mammals and birds appear? 500,000,000 years ago
200,000,000 years ago
100,000,000 years ago
50,000,000 years ago

What kind of action is a cause of air pollution

The term used to describe a disease-causing microorganism isa. virus.b. infection.c. pathogen.d. microbe.e. bacterium.

How did alexander fleming’s research solve a societal problem? he developed ways to treat inherited diseases. he advocated for regular hand washing to kill germs. he discovered a new type of medicine that could treat infections. he discovered the cause of mad cow disease, an emerging disease.