求下列数式之值：
（1+3+5+…+2009）﹣（2+4+6+…+2008）
解：（1+3+5+…+2009）﹣（2+4+6+…+2008）
=1+（3﹣2）+（5﹣4）+…+（2009﹣2008）
=1+1+1+…+1
=1005
walk，never，exercise，life，clean
Emma is very busy in the moming. She gets up at half past five. After brushing her teeth, she ____. She usually does sports for thirty minutes. Next, she helps to make breakfast. At half past six, she eats breakfast. For breakfast Emma usually has bread and milk. She____ eats hamburgers. Hamburgers are unhealthy. Emma needs a healthy ____. After breakfast she____ her room. Then she goes to school. Emma usually____to school. She says walking is good for her.
下列属于生物的是（ ）
①杨树 ②香菇 ③珊瑚 ④珊瑚虫 ⑤生物化石 ⑥病毒．
