Asweallknow，__________oftheearthsurfaceiscoveredbywater．（）A.ThreefoursB.ThreefourthsC.ThirdfoursD.Thirdquarters

　　As we all know，__________ of the earth surface is covered by water．（）

　　A.Three fours

　　B.Three fourths

　　C.Third fours

　　D.Third quarters