Hello everyone

I have decided to make an application to a CELTA course and I have a written pre-interview taks which I am trying to complete and wondered if I might ask for some advice from a qualified teacher.

The task gives 4 mini conversations and ask me to underline and correct the mistake, and then explain the correction clearly, as if I were talking to a group of beginner level students. I think that I can identify and correct the mistakes but I am a little unsure how to explain the correction in simple terms - can anyone offer me some assistance? I have written an idea of how I might explain the mistake in red but could anyone tell me whether I have done it correctly, or if you can suggest a better way of explaining?

1. "Can I help you?"
"Yes, I've left my luggages on the train"

Luggage is a singular word. You could say "suitcases" or "bags" instead, both of which can be plural, but luggage is always singularly.

2. "Have you got a ticket?"
"Yes, I've bought one last week"

I'm a little unsure how to explain this one. You would say "Yes, I bought one last week". The 'have' is unnecessary, but I don't know how to explain why?!

3. "Has Sarah been ill? She has lost a lot of weight"
"Yes, she's really slender now, isn't she?"

Slender is a word which is associated with looking well and healthy. The question implies that Sarah is not well so a more suitable word to use would be 'thin'.

4."Why didn't you phone me last night?"
"Because I did my homework"

The reply should be 'because I was doing my homework' which suggests that the person was actually in the process of doing their homework at the time they could have been making the phonecall. Again, I am not sure how to elaborate on this so any help would be fantastic.

Thank you very much for reading this. If anyone can offer me any suggestions on even one or two of the questions then I would be very grateful.

Thank you very much,