Question

Read this sentence:

I bought this stupid bike a month ago, and the tires are already flat.
Which is an appropriate way to rewrite this sentence for a business letter?
A. Within one month of buying this bike, the cheap tires you used have already gone flat.
B. The tires you put on your bikes are no good and go flat in less than one month.
C. Though the bike is fine, people generally enjoy having tires that don't go flat in one month.
D. I bought this bike one month ago, and, unfortunately, the tires have already gone flat.