to be

[Ned_Marian]

Give me pleae some explanations about using "to be" in the following phrase, and someone is wrong:

1. That can be an opportunity to demonstrate their skills.
2. That could be an opportunity ...
3. That could have been an opportunity ...
4. That could had been an opportunity ...

Let me give you an context and tell me what expression above is correct?

Someone report about a selection for a job that happend in the past. The next round is a practical one. He wants to say this round "could be ?" an opportunity for candidates (if they are focus) to demonstrate their skills.

How do he report about this event?

[Dozy]

#4 is ungrammatical, so we can ignore that one.

Your explanation of the context is not very clear to me. You say the job selection happened in the past, but then say "the next round is a practical one" as if this round is in the future.

If "the next round" is the future then you would normally say "This could be an opportunity for them to demonstrate their skills". "This can be an opportunity..." is not impossible. (Of course, you could also simply say "This is an opportunity...".)

"That could have been an opportunity..." implies that a past opportunity was missed. The plain way of talking about a past oppportunity would be "That was an opportunity..."

[Ned_Marian]

The practical round happened also into the past, but in the future related to one theoretical one.
Maybe I had to say "the next round was a practical one".
My confusion is when someone try to report a situation from the past but in the future related to the other.
If in the present I say:
"That can be an opportunity to demonstrate their skills" or "That could be an opportunity to demonstrate their skills".

how are this sentence transformed when someone report from the past? .... but It was incert (at the moment of speaking) that the opportunity was missed.

[Dozy]

I'm sorry Ned, I don't really understand your question. I have no idea what you mean by "in the future related to one theoretical one" or "...when someone try to report a situation from the past but in the future related to the other."

If you are talking about a future opportunity, you can say "This could be an opportunity...". If you are talking about a missed past opportunity, you can say "That could have been an opportunity...". This is basically the same answer as I gave before, so I'm not sure how much help it will be.

[Ned_Marian]

Take in consideration the last part of my post starting with "If in the present I say: ..."

[Dozy]

I don't understand how that is different from talking about a past missed opportunity. Perhaps it would help if you tried to explain why the sentences I have suggested do not work in the situation you are imagining. For example, why does "That could have been an opportunity..." not work?

[Ned_Marian]

Until now I understand the phrase "That could have been an opportunity ..." express a missed opportunity.

I will try again explain my situation, and tell me if the above variant work.

First I will describe te situation in present, and after that the situation have to be reported by a reporter.

The situation in present:
It have just ended the first round of the selection. Now I will come the practical one. The candidates become nervous. That could be an opportunity to demonstrate their skills. Some of the candidates could do that some of them couldn't. There is uncertain. I can not say it will be a missed opportunity.

I will try to report the above situation, after the selection ended:
It had just ended the first round of the selection. Now It would come the practical one. The candidates became nervous. That could have been an opportunity to demonstrate their skills. Some of the candidates could have done that some of them couldn't. There was uncertain, I could not say it would be a missed opportunity.

Please tell me if the situation is reported correct. Is it a missed opportunity or an uncertainty in the situation described above?

[Dozy]

"The first round of the selection had just ended. Next would come the practical test. The candidates became nervous. This was an opportunity for them to demonstrate their skills."

(This is what I meant earlier by "the plain way of talking about a past oppportunity", i.e. without any connotation of whether the opportunity was taken or not.)

[Ned_Marian]

Thank you very muck for the explanation and correction.