[解析]
81 Who did it?补全对话:根据上文"I heard someone play the violin."及下文答语"I did."可知,此处应提问谁演奏了小提琴?根据语境应使用过去时.故填Who did it?
82 How often (do you play it)?补全对话:根据下文的答语"Twice a week."可知,应提问频率:你多长时间演奏一次?根据语境应使用一般现在时态.故填How often (do you play it)?
83 Many things 补全对话:根据上文提问"What else do you do in your in your free time?"及下文追问"Like what?"可知,此处的答语应该是:许多活动.故填Many things
84 What about you?补全对话:根据上下文的语句内容我除了做家庭作业外,我还得上许多课外的课,我没有时间做其他的事情来放松自己可知,此处应提问对方:你呢?你在空余时间做什么?故填 What about you?
85 Thank you 补全对话:根据对话上文针对没有时间放松提出一些建议,下句"I'll have a try."可知,此处应对相关建议给予肯定,故可以填Thank you