Read the following context and choose the best option to answer the question.
Context: I really thought it was more recent than that , but I knew it was before they took over Scotty 's and that I had at least two flats and patches since getting that set of tires . With luck the new tires are replacing ones that were patched , but who knows , since I get them rotated regularly . There real surprise was that three years and four months only translated into 20,000 miles , even with all of the travel I have done ! ! The Tire Depot people thought I had a good attitude about it all , but I was just grateful it happened now and not while I was on the road .
Question: Why did the narrator have to replace their tires ?
Options: 
A. None of the above choices .
B. Because they frequently rotate their tires .
C. Because they put a lot of mileage on them at work .
D. Because all four tires had gotten a flat .


C