单项选择题 It was（）that his faith in the Government was severely shaken.

单项选择题 She was speaking to a crowd when she（）someone called her behin.

多项选择题 氯气系统防护措施有（），进入着火现场，应穿自供氧式呼吸装备的防护服，防止因缺氧发生危险。