Which event in act iv foreshadows macbeth's eventual downfall?

The answer is Macduff discovers Macbeth has murdered his family and vows to kill Macbeth himself. This  is used to foreshadow an imminent conflict between Macbeth and Macduff.

good luck!!

i don't know sorry i cannot read a novel in 30 min.

explanation:

but just in case i think the answer is b.

the examples that saki used to represent satire through situational irony are options two (2) and five (5) inasmuch as the wolf thought that looking for a girl in the bushes could be as easy as hunting little pigs at the park, but it took him so much time to find the girl if it had not been not for a silly mistake. also, bertha would have survived to the wolf's hunt if she had not won those medals for goodness, which at the end they were what got her killed by making noise, so winning medals of goodness was not so good achievement, after all.