Why did orochimaru ask? He is not a rambler. It can be estimated that orochimaru's blood type is type A. At this time, the dissatisfaction in his eyes shows that he has the purpose of taking sinus as the reincarnation object, but type A blood can't be transfused with AB blood, and AB blood can accept any blood type, which also laid a theoretical foundation for Dou to bear orochimaru's remains later.