Select from options: Continue writing the next sentence.

How to dress for hiking
Avoid heavy base layers if you plan on hiking in warm weather.
Long underwear is smart for colder weather, but it does not make much sense if you plan on hiking through the woods in the middle of summer.
Wear the right thickness of thermal underwear for cool weather.

Pick your answer from:
(a). There are a number of types of thermal underwear, including : If you want less warmth, choose a heavier set of thermal underwear. Synthetic materials may not be the best option for cooler weather, but they are a great alternative if you want a tighter fit.
(b). Thicker underwear provides tighter protection and creates a tighter fit when you hike. Avoid wearing too thick underwear if possible because thicker underwear can wear out your legs faster.
(c). Thermal underwear is a bit more important for hot weather. As long as you don't sweat or get chilled, a thicker " thick " thermal underwear is more sensible than thin.
(d). Thermal underwear comes in light, mid, and expedition weights. The colder the conditions and the longer you plan on being out in them, the heavier you should go with.
Answer:
(d).