Oxygen tanks can explode if the gas is ignited. why is this? a. oxygen is not flammable b. oxygen is flammable c. oxygen causes an arc flash d. oxygen releases thermal energy

(1) fire extended humans’ geographical boundaries by allowing them to travel into regions that were previously too cold to explore. (2) it also kept predators away, allowing early humans to sleep securely. (3) fire, in fact, has been a significant factor in human development and progress in many ways. (4) other obvious benefits of fire are its uses in cooking and in hunting. (5) probably even more important, however, is that learning to control fire allowed people to change the very rhythm of their lives. (6) before fire, the human daily cycle coincided with the rising and setting of the sun. (7) with fire, though, humans gained time to think and talk about the day’s events and to prepare strategies for coping with tomorrow. the sentence that expresses the main idea is: (type the number of the sentence. then click “go.”)

Read the passage first of all if someone says your dream is impossible, they’re wrong. you can’t prove that something is impossible-all you know is that[it] hasn’t been done yet. people said no one could scale mount everest but in 1953, sir edmund hilary and tenzing norway gazed down upon the world from it’s summit. people said that man could not fly, but in 1903, orville and wilbur wright made the first sustained powered flight in a heavier-than-air machine. people said, “okay, we admit that someone could climb mount everest, and we admit that man has learned to fly, but no one will ever, ever walk on the face of the moon.” if we can send three men a quarter of a million miles away and bring them home safely, is there any great task we cannot accomplish? which identifies the textual evidence that best supports the claim: the authors purpose is to persuade? a: the author shares historical information about the wright brothers. b: the author states that men have walked the moon. c: the author states that others who think your dreams are impossible are wrong. d: the author wants to know what tasks we cannot accomplish.

According to warren in the brown opinion, how did conditions change between the time the fourteenth amendment was adopted and the time the supreme court considered brown v. board of education?