有个句子原句是：This place must have been prosperous when people were still living here.能这样说吗？This place must have been prosperous when people had lived here.请问：had lived here 是曾在这里住过还是已经住在这里？
large parts of the online economy are fuelled by data that consumers spray around without thought.这句话中， spray 和around之间是省略了data吗？without thought是从句成分还是主句成分跟在data后面？
The guard rails that will be familiar to anyone who has attempted to cross a road were an engineering solution to pedestrian safety. 句中的has attempted换成attempted有什么影响一直感觉完成时和过去时的区别似懂非懂谢谢解惑
...his will be tapered off 2-4 weeks after you commence cyclosporine at which time, you can stop the corticosteroids, but continue Cyclosporine and artificial tears. 是Cyclosporine使用说明里的一句话，前后文大意是说刚开始使用Cyclosporine药的时候需要先配合 cortic...
原句：A desire to sell gold appeared to have been worsened by thinking that concerns about the Greek economy have somewhat eased. 此句中可以用appear to be 吗？Appear to have done 和appear to do 有何区别？谢谢老师精彩解答。
...d is kept in the living room.It has belonged to our family for a long time.The instrument was bought by my grandfather many years ago.Recently it was damaged by a visitor.She tried to play jazz on it! She struck the keys too hard and two of the strings were broken.My father was s...
①He must have left Beijing,（hasn't he?）②A：Those tomatoes are huge!You must have watered them a lot! B：Yes,I （did）.They ought to be ripe enough to pick by next Friday.为什么①用现在完成时，②用一般过去时，②能不能用“Yes,I have.”？