Today we focus on _____ is called recurrent obesity (复发性肥胖) or yo-yo obesity (溜溜球式肥胖), _____ is the phenomenon _____ we gain weight and then go on a successful diet, but within 12 months we go back to our original weight.

A、what; which; in which

B、which; which; where

C、all; that; that

D、whatever; as; which