话题 a value

话题 a few

话题 quite a

话题 a knowledge

话题 a-

话题 a hundred

话题 a bread

话题 a thing

话题 前缀 a-

话题 a family

用户 a卡卡

用户 大力A

问题 改错题中的the chance of a lifetime不理解

下面一句是2010年全国I卷高考英语的短文改错题：It was the chance of a lifetime to win the first ...答案是划掉 lifetime 前的 a。但这在牛津字典上不是一个固定用法吗，a 是固定的，应该不能删除或改为 the 吧！

问题 Being a political science major, ..... (以Being开头的句子是什么用法)

Being a political science major, he started his career in a government office as a junior clerk.请问老师们，这里Being是什么用法？

问题 one和a（an）的用法区别

老师好，请问一下：While there are many positive developments associated with the Internet, there are also certain fears and concerns. One concern relates to...此处的one不能用a的原因是什么？是one区别于a的什么用法？