Whenever Dylan walks into his room, his roommate loudly blows an air horn, which startles Dylan. Dylan doesn't think this is funny, and after several such episodes, he tenses up and opens the door more slowly and carefully. In this practical joke, Dylan's reflex of tensing up whenever he opens the door is the .

Isobars are lines of constant or equal pressure on a weather map. they can be used to find areas of low or high pressure over a broad area, and they can tell us how intense the system may be. on weather maps, you may have noticed areas that have a large l or h over a region with lines circling around them. the l stands for low pressure and h stands for high pressure. the lines circling them are isobars. check out the pressure system and isobars over georgia and florida. what is the present weather in this area ? a) clear and sunny b) cold and cloudy c) changing weather d) lots of precipitation