【多选题】斯捷的纳维亚国家包括北欧五国,即( )。
【单选题】She writes ___ from time to time.
【简答题】食品中的酸主要是 __________酸 。
【单选题】In winter people usually keep flowers in their houses to them from the cold weather.
【单选题】It is better to teach a man how to fish than ____________ him fish.
【简答题】食品中的酸主要有两类,即()和无机酸,其中主要酸是()。