Answer
B.
Work Step by Step
The pollen grains genetically S5 would fail in pollination due to the self-incompatibility mechanism, but the S2 pollen would succeed, having no match in the plant being pollinated (B.). A. is wrong because it ignores the self-incompatibility issue, and C. is incorrect since sporophytic incompatibility would not allow half to successfully pollinate. D. is untrue since S2 pollen should be able to work.
