Concept:A past tense verb like "complained" needs another past tense expression to complete the sentence correctly.Explanation:The word "complained" shows that the action happened in the past.So the missing words must also be in the past tense."Could not hear" correctly expresses a past inability to hear.The other options use present or continuous forms that do not match the past time frame.Therefore, the best completion is option B.Answer:B. could not hear