Which of the following could cause changes in populations of organisms over time? a. The environment c. Human choices b. Geographic separation d. All of these.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

not only is it colder, it also becomes darker, less salty, and more dense.

yes

no

blue is scattered more than other colors because it travels as shorter, smaller waves. this is why we see a blue sky most of the time.