一、语法选择（共15小题：每小题1分，满分15分）
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，从1-15各题所给的A、B、C和D项中选出最佳选项，并在答题卡上将该项涂黑。
Cold weather during winter months may keep many people from 1 home and running in the open air. 2 , a new study shows 3 the drop in temperature is a good reason to run. In fact, researchers say, running in cold weather 4 improve one’s performance（身体机能）. Many people say running in winter is difficult. Two reasons are the low temperatures and bitter winds. Yet many runners might find 5 easier than running in hot weather. That could be because lower temperatures reduce stress on the body. When you run in cold weather, your heart rate is 6 than in warmer conditions. Besides, the body needs less water 7 a cold day than in warm weather. This information comes from John Brewer, a sports scientist at St. Mary’s University in London. Brewer says every movement runners make produces heat. He explains that one way in which we
