单选题 (Those of us) who work in chemical (laboratories), should have (their) lungs (checked) quite regularly.
  • A. Those of us
  • B. laboratories
  • C. their
  • D. checked


【正确答案】 A
【答案解析】人称一致错误，应改为Those。主语是在化工厂工作的人，对应后面的代词their。