don't talk until you _(tell) to.

題目：

don't talk until you _(tell) to.
the meeting _(hold)in the school hall _(host) by our headmaster yesterday evening

解答：

don't talk until you are told_(tell) to.
用被動語態
再問： the meeting _(hold)in the school hall _(host) by our headmaster yesterday evening
再答： held (過去分詞作定語) was hosted（謂語動詞，用被動） 昨天晚上在學校大廳召開的會議是由校長主持的。