My grandpa is in his seventies. He’s ____ to take the bus for free.

A．old enough

B．enough old

C．young enough

D．enough young

下列哪项因素与超急排异反应无关

A．受者预先抗体形成

B．ABO血型不相溶

C．淋巴细胞毒性实验阳性

D．HLA配型不理想

E．发生于术中肾血循环恢复后数分钟或数小时内