The correct answer is c. Genetic Variation. Bacteria are very numerous, ad random mutation of bacterial DNA generates a wide variety of change, including resistance.
Mountain range; when plates are pushed together, they cause rock to push up. After thousands of years, a mountain will be formed after the molten rock cools.
Carpool to work,ride the bus,or switch to electric cars.
B. The nervous system collects and responds to information about the external and internal environment.
