Select the correct subordinating conjunction to complete the sentence.. he did to study for the final exam must have been ; his grade improved from a b to an a.. a. which. b. that. c. so what. d. whatever.

I think the correct subordination conjunction to complete the sentence would be : D. whatever

Whatever he did to study for the final exam must be have been helpful; his grade improved from a B to an A. The other one seems not to make any sense

hope this helps

"marigolds" takes place in a shantytown in rural maryland during the great depression.