since引导的时间状语从句主句用延续性还是瞬间性动词

这样看主句是表肯定还是否定：（可参考下面解析）1．若since引导的状语从句的谓语是终止性动词的过去时,则从句表示的时间是“从动作开始的那一时刻起”.例如：He has studied very hard since he came to our school...