Collisions between galaxies are thought to Group of answer choices have stopped about 5 billion years ago. be commonplace. have only occurred between 10 and 15 billion years ago. be extremely rare. have never occurred.

As seen in a us weather map, the h (or high) and l (or low) symbols indicate regions where surface air pressures are high or low, respectively, compared to surrounding areas. an h is plotted where the air pressure is highest and an l is plotted where the air pressure is lowest. proceeding outward and away from the center of a high pressure system, the air pressure "