设a，b，c为实数，.记集合S=若cardS,cardT分别为集合元素S，T的元素个数，则下列结论不可能的是（  ）

A．cardS="1," cardT="0"	B．cardS="1," cardT=1
C．cardS="2," cardT="2"	D．cardS="2," cardT=3