题目

计算： 答案：解：原式＝8﹣4+1﹣（2﹣1）（2+1）+2﹣ ＝8﹣4+1﹣（12﹣1）+2﹣ ＝8﹣4+1﹣11+2﹣ ＝﹣4﹣．When the H1N1 virus____ at first in Mexico, no one had the least idea that it would spread so rapidly throughout the worldA.broke offB.broke downC.broke outD.broke away