问题
选择题
_____ of their bad habits, the boys switched from being dependent on their parents to _____ for others.
A．Having rid; sacrificing
B．To rid; sacrifice
C．Rid; sacrificing
D．Having been rid; sacrifice
答案
A.
本题考查非谓语动词。句意：通过摆脱坏习惯后，男孩们从依赖父母的人变成了可以为他人牺牲的人。the boys是rid的执行者，要用现在分词的主动形式，排除C和D。switch from…to... （从……转向……）中to是介词，后跟doing。