- 一道选择题tohelppatientsandsavetheirl
- to help patients and save their lives _____ a doctor's duty.
a.be
b.is
c.are
d.to be
为什么谓语动词用单数呢，谢谢
- 选B
该句的主语不是patients也不是lives
该句的主语是to help patients and save their lives
因此需要用谓语动词单数
to help patients and save their lives _is_ a doctor's duty.
帮助病人并拯救他们的生命是医生的职责。