题目

Great Activities for Nature LoversHikingOne of the easiest and most accessible ways to get close to nature is by setting out on a good old fashioned hike. Hiking generally doesn’t require any fancy equipment or special skills, just a piece of map and a thirst for adventure. This activity can be as relaxing as you make it.Backcountry CampingWhy limit yourself to just a day hike when you can have a full weekend (or longer) adventure? Backcountry camping involves packing your tent, sleeping gear, food, and water on your back to set up camp in a remote location. If you’re an experienced hiker 下列气体既能用浓硫酸作干燥剂又可以用氢氧化钠作干燥剂的是(  ) A. NH3　　　　    B. O2　　　　　　   C. CO2　　　　　　 D. SO2