This question has options. Answer the question about text:

I just spent a solid whack of time in the mountains , six full days out of the last eight hiking in Garibaldi Provincial Park . And I could n't be happier still feeling the burn in my legs . It started last Sunday with a 30-plus kilometre day trip into the Diamond Head area .

What is causing the narrator to be presently so exhausted ?
Pick your answer from: (a). None of the above choices .. (b). They could n't get to bed .. (c). They did not sleep the night before .. (d). They just hiked a great distance ..
(d).