48.threat Their lives were frequently ___ by gas explosion.49.perform The first American ___ of
问题描述：
48.threat Their lives were frequently ___ by gas explosion.49.perform The first American ___ of
答
1.threatened
句子的意思是：瓦斯爆炸时刻威胁着他们的生命.
2.performance
根据句子,横线中应该填名词,perform的名词形式是performance.