Answer:
I'm pretty sure it's a. With refrigeration you do have more food variety, the food lasts longer so less waste.
Human activity can affect the river ecosystems because first of all humans take the water and use it for themselves, they also pollute it, disturb the ecosystems and kill fish or oysters etc. in the ecosystems.
Medulla oblongata is the part of the brainstem that controls the autonomic functions such as sneezing, coughing, digestion and etc.
