几何相似要求流场内( )。 A.对应角度相等 B.对应线段成比例 C.A、B同时 发布时间:2017-12-03 05:25 │ 来源:www.tikuol.com 题型:单项选择题 问题: 几何相似要求流场内( )。A.对应角度相等 B.对应线段成比例C.A、B同时满足 D.A、B同时满足,且对应点速度成比例
题型:单项选择题 Stress is with us all the time. It comes from mental or emotional activity as well as physical activity. It is unique and personal to each of us. So personal, in fact, that what may be relaxing to one person may be stressful to another. For example, if you’re a busy executive who likes to keep occupied all of the time, "taking it easy" at the beach on a beautiful day may be extremely frustrating, nonproductive, and upsetting. You may be emotionally distressed from "doing nothing." Too much emotional stress can cause physical illnesses such as high blood pressure, ulcers, or even heart disease. Physical stress from work or exercise is not likely to cause such ailments. The truth is that physical exercise can help you to relax and to better handle your mental or emotional stress.One method mentioned to help handle stress is ______.A.physical exerciseB.tranquilizersC.drugsD.taking it easy 查看答案
题型:单项选择题 下列表格内数值表示某人工池塘生态系统一年内主要营养级的能量,下图方框内表示该池塘生态系统的主要食物链,其中a表示一年内该营养级生物总能量,b表示一年内该营养级生物同化的能量。分析回答:该生态系统内既有捕食关系又有竞争关系的两种生物是()。 查看答案