英语中从句的时态问题：
一、当主句是一般现在时,从句可以根据需要使用任何一种时态.
例如：I think that he likes apples./She says that her mom was ill.
二、当主句是一般过去时,从句则要使用过去的某种时态（时态呼应）
例如：I thought that he liked apples./She said that her mom had been ill.
I started to think Beijingthe 2008 Beijing Olympic Games is far.这句话中由于主句用了过去时,所以从句也要用过去时,所以是was.