thE DnA in thE spErm CElls CAn BE mEAsurED ________.
A．in thE sAmE wAy how thE CAttlE ArE hErDED
B．whEn thEy pAss through A tuBE onE BEhinD thE othEr
C．AFtEr thEy pAss through A lAsEr tuBE
D．whEn thEy ArE sCAnnED By A lAsEr DEtECtor All At A timE