Which is the best meaning of the word 'incompatible'?

Directions: Complete the passage by filling the most suitable option from each list.

Human to human blood transfusions in the nineteenth century were plagued by two major problems: first, the necessity of transfusing blood as soon as it was drawn and second the occasionally fatal reactions, often accompanied by fever or nausea, which afflicted many patients. Rudimentary anticoagulants were developed as early as 1860, solving the first obstacle. Later advances in the blood analysis revealed not only that there are blood groups with which donors may be incompatible but also that white blood cells-----------24------ new blood from even seemingly suitable donors.