Question

If ____ in, the viruses can result in illness or even deaths.

A．breathed

B．to breathe

C．breathes

D．is breathed

Answer 1

A

考察非谓语动词。Breath的逻辑主语是viruses，被动关系，所以选择breathed="the" viruses are breathed in,
句意为如果被吸入体内，这些病毒能致病或者致死。