①将图中的集气瓶分为5等份,并作好标记.
②在带橡皮塞和导管的燃烧匙内装入足量的红磷,将导管上的止水夹夹紧,在酒精灯上点燃红磷,并立即伸入集气瓶内,塞紧橡皮塞.
③充分反应后,待集气瓶冷却至室温,打开止水夹.请回答下列问题:
已知f(n)=1+3+5+…+(2n﹣5),且n是大于2的正整数,则f(10)= ____.
I was late for school this morning because the traffic was ________ by an accident. ( )