I think it is just specifying A time, not saying that that is the current time, so Duo doesn't like your "It is" before the time expression. I also think you might need a space before the "am" to separate it from the 8:45.

Maybe you need a space between the 45 and the am... It accepted my answer of 8:45 am.

I think that would be 现在上午(8.45)。So you would say "now" before stating the time.

I think it's becuase you didnt specify "morning" where it says "上午"

Exactly, this should definitely be accepted

The sentence is not correct if 'it is' is not used. The correct sentence in English is: It is 8:45 in the morning. The English sentence given by Duolingo is wrong.

It is not a complete sentence, but a phrase. So it could be better to use that one.

Because there is no context to imply that it is 8:45 am.

Correct. 早上 = morning. 上午 lasts until noon.

The former is for early morning, the latter is for late morning. I forget the approximate cutoff, but I think I learned it's usually like 10. Either way, it's not a hard distinction.

They are pretty much the same. 早上 is just more of "morning," while 上午 is before noon. There really is no difference, it's just used in different contexts.

That's what I thought.

I did the same - you should give instructions about whether it's acceptable to use numbers/letters

Exactly!

Yes, I agree the pronunciation isn't very clear.

Not to be picky but Side note: "hear" is the proper use of the word.

I totally heard xiawu

That is not really how it is said in English, although the meaning is clear enough.

In the morning at 8:45 ist also not accepted by DuoLingo.

点 is used to mark time and hours.

Yes, the Chinese is also not a "complete" sentence.

现在是八点四十五分. = "It is (now) 8:45 in the morning".

idk :/

Look above.

In English "8 hours 45 minutes" is how you specify the duration of a period of time, not how you specify the actual time.