消防员们戴上面具以保护自己免受有毒烟雾的伤害。

The firefighters wore a ___mask to protect themselves from the toxic smoke.

窃贼们在抢劫过程中使用面具来隐藏身份。

The thieves used a ___mask to hide their identities during the robbery.

每个人都戴着精美的面具去参加化装舞会。

Everyone wore an elaborate ___mask to the masquerade ball.