Before infusing stem cells into a patient, processing may be necessary; for example, if the donor and recipient have a major blood group incompatibility, red blood cells may be removed from the graft to prevent a transfusion reaction from occurring.

A: have a major blood group incompatibility, red blood cells may be
B: had a major blood group incompatibility, red blood cells will be
C: have a major blood group incompatibility, red blood cells are
D: will have a major blood group incompatibility, red blood cells will be
E: have a major blood group incompatibility, red blood cells would be

[spoiler]The OA is C. However, if the beginning of the sentence suggests that 'processing may be necessary' shouldn't the underlined part of the sentence convey the same idea? Please advise.[/spoiler]

Regards,
Amit