Explanation:
They can't tranfuse because they will have an ABO incompatibility reaction. In an ABO incompatibility reaction, your immune system attacks the new blood cells and destroys them
If you have type AB you have both A and B antigens. Therefore you have B too that's why you can't only tranfuse with A after all you have to have to have both types.
I think the answer is evolution.
The complementary strand is
taaccgat
T -A
G-C
Always!
