Question

What a wonderful city this is! (Change into Assertive.)

Answer 1

heya!
here's your answer!
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as we can see in this question we have to change this given sentence into assertive sentence.

before changing anything we must know what and assertive sentence is:-

assertive sentence : in simple words and assertive sentence is a simple sentence having a subject or predicate and a full stop as the most common punctuation mark.
it is a straight forward sentence with no exclamation.

required answer will be:-

This is a wonderful city.

some important things that need to be noted are that the sentence should start with a capital letter and the nouns too.

and it should always end with a full stop.

Hope this helps you:)

Answer 2

Exclamatory sentence:

   What a wonderful city this is !

  Exclamation is about the city.

To change into Assertive sentence, we start with the phrase "this is". That appears at the end of the exclamation.

   This is a wonderful city.        -  correct answer

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If the exclamatory sentence is:
            How wonderful this city is !

   The exclamation here is about "wonder" or "being wonderful".

Then  our affirmative sentence will be:
           This city is wonderful.