Answer:
Whatever
Step-by-step explanation:
The correct term that best fits the incomplete sentence is 'whatever.' Read the following sentences and you will be able to determine that the term 'whatever' is best.
Which he did to study for the final exam must have been helpful; his grade improved from a B to an A.
That he did to study for the final exam must have been helpful; his grade improved from a B to an A.
So what he did to study for the final exam must have been helpful; his grade improved from a B to an A.
Whatever he did to study for the final exam must have been helpful; his grade improved from a B to an A.