present perfect + past perfect

[Monte]

Hello,
Is it possible to use present perfect and past perfect in one sentence?

According to my grammar book I must say:
1. I explained that I had forgotten much of my school English.
2. I asked them why they had not finished.

Can I do it this way:
1. I have explained that I had forgotten much of my school English.
2. I have asked them why they had not finished.


Thanks!

[bhaisahab]

Hello,
Is it possible to use present perfect and past perfect in one sentence?

According to my grammar book I must say:
1. I explained that I had forgotten much of my school English.
2. I asked them why they had not finished.

Can I do it this way:
1. I have explained that I had forgotten much of my school English.
2. I have asked them why they had not finished.


Thanks!

No.

[Monte]

And can you please explain me why? Is it because present perfect has a connection with the present?

So, when I use past perfect it must be combined with past simple?

[Raymott]

And can you please explain me why? Is it because present perfect has a connection with the present?

So, when I use past perfect it must be combined with past simple?

Yes it is possible to use those tenses together, if that's what you mean. None of your sentences give any context to show why any particular tense should be used though.

Here's one example:
A: I failed the test because I hadn't eaten breakfast beforehand, and was not thinking well.
B: Why don't you tell them you hadn't eaten breakfast? They might be lenient.
A: I've [already] told them I hadn't eaten breakfast!

[bhaisahab]

1. I have explained that I had forgotten much of my school English.
2. I have asked them why they had not finished.
What I should have said is that these two sentences don't make much sense as they stand.
Sorry for my abrupt "No."

[Monte]

Thank you very much!