It demonstrates natural selection since the the bacteria that are resistant are selected for because they are the ones that survive. These resistant bacteria -since they are still living- multiply (thus leaving "offspring") and are able to keep their species in existence which adds to their fitness.
A theory is a set of sentences which is closed to make logical implications.
Answer: The answer would be B
Explanation: deep-ocean currents are driven by differences in the water's density, which is controlled by temperature.
Hope this helps!
~Jarvis
They are responsible for the detection of odorants which gives rise to the sense of smell