In questions like this one , you should first read the passage and then read the instructions. DO NOT read the alternatives. Then , with the information you got from the passage , try to awnser the question without looking at the alternatives. Now compare your awnser to the alternatives and eliminate the ones you are sure are wrong.
From the passage you learn that light pollution , caused by man-made lights , sometimes creates fogs and hazes that make the night sky look like a "dark sheet of paper". If you compare what you understood from the passage to the alternatives , you ll realize that A) is the one that makes more sense and its more compatible with your awnser. If you eliminated all alternatives you could but there still are 2 choices remaining and you are not sure which one it is , go back to the passage and try to find evidence for each alternative and try to eliminate one of the alternatives
the hotter water flows to the top and the colder water flows down which then gets heated goes back up and the hot water that went up is colder again so they keep flipping
