Write a question about the following article.

The run in the gym on Friday was a rather tough one . I ' m not so sure why , but my legs just felt sooo heavy!But I pushed on at 8.6 KPH all the way through . I was going to increase the speed later but could n't , so it was a slow run . After 20 - 25 mins , I think then I thought I will try run 5 K ... so I did ! I was quite glad I did it in the end .

Question:
Why would the narrator 's legs be feeling so heavy ?
Choices:
(A). They have been injured ..
(B). They are a paraplegic ..
(C). They have been running from cars ..
(D). They have been overtraining ..