UNIT 7 – WORLD POPULATION CHOOSE THE WORD THAT HAS THE UNDERLINED PART...

18. We didn’t know your sister was ill, so we didn’t visit her.

a. If we knew your sister was ill, we would visit her.

b. If we had known your sister was ill, we would have visited her.

c. If we know your sister was ill, we will visit her.

d. Unless we know your sister was ill, we won’t visit her.