when、where、why作关系副词,引导定语从句,表“在……的时候”、“在……地方”、“……的原因”。例如:1.It’s about a time when there were black slaves in North America.(when的先行词为time(时间名词),when作状语,相当于during the time。)2.As a child he used to work hard and helped his father on when, where, why for the relationship between adverbs, guide attributive clause, table “in the time ”, “in ... place ”, “... ... the reason ”. For example: 1.It’s about a time when there were black slaves in North America. (When the antecedent is time (time noun), when is an adverb, which is equivalent to during the time.) 2.As a child he used to work hard and helped his father on