Read the following context and choose the best option to answer the question.
Context: I ran my five - mile rest run today and enjoyed being out . My wakeup heart rate was 55 , a bit higher than normal , but I felt fine . I was out earlier , and the temperature was 75 ( F ) when I left home . However , I spent half an hour watching two guys fly a RC dirigible , so the temperature was probably about 80 when I started running .
Question: What may be the reason they consider 55 beats per minute to be high for them ?
Options: 
A. They run , so their heart rate is normally lower .
B. They are n't active so their heart does n't have to work as hard .
C. None of the above choices .
D. They sit , so they do n't need to work as hard .


A