You’ll start having positive results you replace negative thoughts with positive ones .
A. since
B. unless
C. until
D. once
网友回答
A. since
B. unless
C. until
(答案→)D. once
解析:句意:一旦你用积极的思考代替消极的思考,你将开始有积极地结果。since自从,引导时状语从句;unless除非,引导时间状语从句; until 直到,引导时间状语从句;once一旦,引导条件状语从句。根据句意前后是条件与结果的关系,因此用连词once来引导。故选D。