A. Because grapes and pumpkins grow on vines so they work together. With B., it's either your parents OR your grandparents, not both, therefore they are not working together. For C., Steve and Thuan love professional basketball, but love is a noun. There is no verb in D., so the answer is A.
A. Because the realities of today's world are causing many women to reassess their values and hopes, which will be a positive development in this country.
Something isn't in the right order, because the paragraph isn't well organized I don't know where the answer choices are supposed to be located.