An Immediate Spin Crossmatch Was Performed Using Recipient Serum and Donor

Multiple Choice

An immediate spin crossmatch was performed using recipient serum and donor cells from a group AB unit. At immediate spin, the reaction was 4+. What is the reason for this positive reaction?

A) ABO incompatibility
B) An alloantibody
C) Positive DAT on donor cells
D) Positive DAT on recipient cells