请教一个对不定式符号to理解的问题

题目

请教一个对不定式符号to理解的问题
我确定不了在句子The implications are plain to see中,不定式符号to所表达的意思.我知道 plain to see 的意思是 very clear.
我看了to在词字典中意思,
■expressing purpose or intention.
I set out to buy food.
■expressing an outcome,result,or consequence.
he managed to escape.
■expressing a cause.
I'm sorry to hear that.
■indicating a desired or advisable action.
we asked her to explain.
等等,所构成的不定式差不多都是起到状语的作用.仔细地看了多遍,可还是确定不了to所表达的意思.

答案

不定式中的to是没有自己的意思的,只是用来作不定式的标志.很多情况下不定式并没有to：Why ask me?You'd better hurry.You made me do it.最后一句如果改成被动语态,就要加to了：I was made to do it.至于不定式在句...