5.由 when 等引导的状语从句,如果主语与主句的主语一致或是 it ,谓语动词又含 be 动词时,主语和 be 动词常常被省略,就变成“ when + V-ing/ V-ed/ adj/ 介词词组”的结构.
如:( 1 ) When in Rome,do as Romans do.入乡随俗.
( 2 ) When (we are ) young,we are full of hope.年轻时,我们大家总是充满希望.
( 3 ) Don't reach sideways when standing on a ladder.站在梯子上时,不要侧着身子去够东西