Task 2 Choose the best word among these comparison and contrast words (填写对应序号)Sleep has always been a fascinating topic. We spend about one-third of our adult lives sleeping. Most animals sleep in a____1____ fashion - they collapse and relax their muscles. _____2_____, birds and horses sleep upright, with their antigravity muscles at work. Most of us complain when we have not gotten several hours of sleep. ____3____ some people sleep for an hour or less a day and lead ____4____ healthy and normal lives.