题目

两种元素可以组成AB2型离子化合物，它们的原子序数可能是A  11和8    B  6和8    C  7和8    D  12和9  答案：D解析: --- It was not until she had arrived home _________ her appointment with the doctor. A. when she remembered                  B. that she remembered  C. did she remember                      D. and she remembered