Give the correct form of the verbs given in brackets

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?