2个英语词组的意思

have no choice but to （do sth.）[简明英汉词典]
v.别无他法, 只好

mistake A for B [简明英汉词典]
把A误认为B

简单明了～～（建议你去下载一个金山词霸2007专业版，很好用）

mistake A for B ”误认为A是B”
have no choice but to do sth ”（别无选择）只能做sth”
=have nothing to do but do

1.将A误认为是B
2.没有选择只能作某事

mistake A for B 把A误认为B
have no choice but to do sth 没有选择,只能去...
例如:
Yesterday,I mistake you for Lily.昨天,我把你错当Lily了.
I have no choice but to answer your question.我没有选择,只能回答你的问题.