求as,though引导让步状语从句的具体用法,最好详细点的,最好有英文例句

as引导的让步状语从句必须倒装;though引导的让步状语从句可以倒装也可以不倒装;e.g.Hard as he tried,he still failed.(他虽然努力了,但仍然失败了.) Though he tried hard,he still failed.Hard though he tried,he...