Gmat
97.Someanthropologistsbelievethatthegenetichomogeneityevidentintheworld’speopleistheresultofa“populationbottleneck”—atsometimeinthepastourancestorssufferedanevent,greatlyreducingtheirnumbersandthusourgeneticvariation.
(A)atsometimeinthepastourancestorssufferedanevent,greatlyreducingtheirnumbers
(B)thatatsometimeinthepastourancestorssufferedaneventthatgreatlyreducedtheirnumbers
(C)thatsometimeinthepastourancestorssufferedaneventsothattheirnumbersweregreatlyreduced,
(D)sometimeinthepastourancestorssufferedaneventfromwhichtheirnumbersweregreatlyreduced
(E)sometimeinthepast,thatourancestorssufferedaneventsoastoreducetheirnumbersgreatly,
为什么选B?