​What,if Anything,is the Advantage of Varying Your Study,instead of Studying

Multiple Choice

​What,if anything,is the advantage of varying your study,instead of studying just one thing at a time until you get it right?

A) Varied study seems easier, although it has no long-term benefit.
B) ​Varied study improves long-term retention, although it seems more difficult.
C) ​Varied study improves short-term retention, although it does not help long-term retention.
D) ​Varied study has no advantage, and several disadvantages.