Literally all I have is humor
<span>the young of a viviparous animal, especially of a mammal, in the early stages of development within the womb, in humans up to the end of the second month.
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It is very easy and simple difference that is antigens and antibodies .
it can be different due to donor and recipient also .
A type blood having antigens
whereas B type blood having nil.
B type blood having antibodies
whereas A type blood having nil.
The second one because they can indicate infection and sickness