Her words were like a sharp knife to his heart
This sentence uses the word "like" to compare two very different things. It is an example of a simile.
She screamed loud enough for the world to hear.
This sentence exaggerates how loud the woman in the sentence screamed. Now matter how loud anyone screams, it's not possible for everyone in the world to hear them. It is an example of hyperbole.
It was an open secret that he was in love with her.
This sentence uses contradiction to make a point about a man's feelings for a woman (that it is an open secret). It expresses a paradox.
His words were as soft as the petals of a flower.
This sentence uses the word "as" to compare two different things. It is another example of a simile.
Answer:
The sentence that uses hyperbole (extreme exaggeration) is option B - she screamed loud enough for the world to hear.