Give the correct form of the verbs given in brackets (0.8pt)    Giải thích                                                                     27. You (call) me when you come home? - Yes, I promise                                                                                         28. I (not understand) what you are saying. Can you speak slowly, please?                                                         29. Will you wait a minute white I (look) through the text?                                                                                       30. Why didn't you stop (think) before you acted?