Choice B is the best answer. Lines 9-10("This······givers") state "This frequent experience of gift-giving can engender ambivalent feelings in gift-givers." In the subsequent sentences, those "ambivalent" feelings are further exemplified as conflicted feelings, as shopping is said to be something that "[m]any relish" (lines 10-11,"engender...because") and "many dread" (line 14,"many...worry").
Choices A, C, and D are incorrect because in this context, "ambivalent" does not mean feelings that are unrealistic, apprehensive, or supportive.