2, xuè is mostly used in written language; xiě is mostly used in spoken language, and often used alone.
3, blood [xiě], group words: chicken blood, blood clots, blood leaching, blood bluff zero lah, blood hutong, blood paste sudden, blood strain, blood heart.
4, blood [xuè], group words: blood, blood type, blood transfusion, taking blood, blood, blood, blood prints, blood gas, blood road, bleeding.