题目

 It is important to keep ______ when you are in danger. A. quiet                      B. calm                  C. silent                     D. still 答案：B新鲜的菠菜放两天就“蔫”了，其中水分的减少主要是因为水发生了（ ）A.液化B.沸腾C.凝固D.蒸发