Choose the correct variant. People who work as firemen ... be brave, as
their job is very difficult.
A) mustn’t B) ought C) shouldn’t
D) should E) are able

People who work as firemen ... be brave, as

their job is very difficult.

D) should

Объяснение:

D) should

Пояснення:

Людям, которые работают пожарными, ... быть смелыми, так как их робота очень сложная.

По смыслу подходить should (следует)