"Isn't" is the best option from the list in terms of completing these sentence. This is primarily because "isn't" is a contraction of the two words "is" and "not.
Dear ______,
I was just writing this to express my gratitude and appreciation! Thank you so much for everything you do! It really means a lot to me and I don't know how I can ever repay you! I am thankful for how you ______, ________, and ______.
Then when you get to the body paragraphs you could repeat one reason you were thankful for them and explain more deeply in each paragraph. Make sure to use a lot of positive adjectives to make it more wordy! Then close of in a closing paragraph. For example....
Again thanks so much for everything! Your kindness means everything to me and everyone around you!
I wish you all the best and more,
_____________
Answer:
As a result and similarly
You go out in danger.
Just to keep us safe.
The pain ,the scares. You've seen it all.
We all thank you for everything you've done to keep us safe.
Dear Veteran, thank you so very much.
I hope this helps and have a wonderful day!
