题目

阅读理解，根据短文内容，从短文后面每题所给的四个选项中选出最佳选项。                                      Mr. and Mrs. Brown have two children, Mike and Liz. The whole family are all busy, so they often leave notes（便条）for each other. Read these four notes of today and answer the following questions. ①     3:30 pm To Mike， Mr. Tyler rang. No football practice today. I’m going to Donna’s house to play and be back at 5:00 pm Liz②     4:00 pm To Liz， It’s your turn to walk the dog. I have to do m下列哪组力有可能为平衡力（ ）①3N、4N、8N ②3N、5N、1N ③4N、7N、8N ④7N、9N、16NA. ①③ B. ③④ C. ①④ D. ②④