學個詞 Learn A Word:2177_effective

　　今天我們要學的詞是 effective. Effective 有效的。The U.S. Center for Disease Control and Prevention says this year's flu shot is less effective because the current flu virus has mutated. 美國疾病預防和控制中心說，由于流感病毒變異，今年流感疫苗的防疫效果可能不是很有效。Indonesia has developed a male birth control pill that is 99% effective. 印度尼西亞開發(fā)出了一種男用避孕藥，有效率高達99%。好的，今天我們學習的詞是 effective, effective, effective...