Hiked Trail C yesterday and really enjoyed it. The park itself lists Trail C as "challenging," though this website only lists it as moderate. Compared to the other trails in the park, this is definitely one of the more challenging ones, but when speaking about hiking trails in general, I agree that "moderate" is a good description. There were several elevation changes, and a couple of challenging uphill climbs involving switchbacks, but it's only about a mile and a half, so it's not too grueling. The views of the pines are lovely, and you even cross over some water a few times. Pay attention to markers so you don't accidentally wander off onto the B or D trail loops, which would extend your hike distance considerably.