i can't walk any longer,Mum.

i can't walk any longer,Mum.
Why?What has happened,dear?(为什么不能用What had happened?）
has happened是现在完成时,had happened是过去完成时,上句用can表明对话是现在时,所以用has happened
Tf you want a ticket for a round trip,you'll have to pay another 80 yuan.(为什么是another,不是其他的?）
another表示3者或三者以上的另一个,根据实际另外再交80应该用another
i don't like this shirt,so iwant to see some others(不应该用another吗）
another+名词单数,前面是some所以加other ones或者others
the crowd is mad with excitement
人们兴奋得发疯
i asked,“where was Marcia's sister?"Can you tell me where Marcia's sister was(用Marcia's sister is为什么不可以）
前面都用was后面只是宾语从句语序正装,时态要和原来一致
i'm sorry to hear that you had a cold last week.i hope that you are well now(用in a good health为什么不行?0
健康不可数,不能加a
lz这么多问题不给分.

1.上一句是一般现在时，不是过去式
2.再付80元，前文并没有提到一个整体，不用其他的
3.前文已有一件裙子了，意思是除了这件以外
4.人群激动的疯了
5.原句中是was啊，改成宾语从句不改变
6.后者强调长时间处于什么状态