第一节（共15小题, 每小题2分，满分30分）阅读下列短文， 选出最佳选项。
Yellowstone National Park is at lofty height. Most of the park is above 2,275 meters.
Yellowstone’s weather is unpredictable. In summer, it may be warm and sunny with temperatures in the high 70s. At night in any given month, the temperature may drop close to freezing. So it is best to come prepared for cold evenings and mornings, especially if you are camping or hiking. When you leave your campsite, please leave it prepared for possible thundershower and wind.
A sunny warm day may become fiercely stormy with wind, rain, sleet and sometimes snow. Without enough clothing, an easy day hike or boat trip can turn into a battle for survival.
Seasonal Weather Information
Cold and snow continue into May, although temperatures gradually climb. Early in spring, daytime temperatures average in the 40s and 50s； by late May and June, they may reach the 60s and 70s. Nighttime lows fall below freezing. Summer
Daytime temperatures are usually in the 70s, occasionally reaching the 80s in the lower elevations (高度). Nights are cool, temperatures may drop in the 40s and 30s—sometimes even the 20s.June can be cool and rainy； July and August tend to be somewhat drier, although afternoon thundershowers are common.
Weather can be pleasant, although temperatures average 10-20 de