Question

4. It was not until the clock struck 12 on TV        firecrackers to celebrate the New Year's coming. (set)

直到电视上敲12点钟，他才燃放鞭炮来庆祝新年的到来。

Answer 1

4. that he set off考查not until句型的强调句。此句为not  until的强调句型，所以后面要用到that。因为是it was，所以强调句的时态是过去时。"放鞭炮"用短语set off。