问题 为什么不能说：A horse is a useful animal.

为什么可以说：正：The horse is a useful animal.正：Horses are useful animals.却不能说：误：A horse is a useful animal. 

问题 as useful 用法

..., Mary seemed to understand that the bigger, heavier hose was "just not as useful."这句话最后的as useful是不是有省略？这里的just什么意思？

问题 using...句式可以用by或者with代替吗

Two fighters freed George using a special type of grease.像这样的句子,using..可以用 by 或者 with 来替换吗?

问题 这里的might have used究竟何意？

...ngs were lacerated. He had poured gently upon me a story that I might have used.困惑：对于句尾的might have used理解问题，这里究竟是表达了对过去的可能性虚拟？ 还是对将来的可能性虚拟呢？故事背景和上下文：me刚刚听完一个He讲述的故事。书...

问题 available, useful, attainable有何区别?

请问 available, useful, attainable有何区别?

问题 available, useful, attainable有何区别?

请问 available, useful, attainable有何区别?

话题 Used to

话题 used

话题 using

话题 use

话题 using copyright

话题 used it

话题 use...as

话题 use...for

话题 as useful