Fill in the blanks with the most appropriate option:-

________ I have finished this exercise. Thank goodness! It was so boring.

At last

The most appropriate option to fill in the blanks is At last.

The sentence "At last I have finished this exercise. Thank goodness! It was so boring." expresses relief and satisfaction that the exercise is finally over. The other options are not appropriate because they do not convey the same meaning.

• The word "together" can be used to refer to two or more people or things that are in close proximity to each other. This does not make sense in the context of the sentence, as the exercise is not something that is done together with someone else.
• The word "just" can be used to refer to something that has happened recently or that is very close in time. This does not make sense in the context of the sentence, as the exercise has been going on for some time.
• The word "exactly" can be used to refer to something that is precise or accurate. This does not make sense in the context of the sentence, as the exercise is not something that is precise or accurate.