The last choice is the answer. Hope this helps!
I assume you mean a simile. A simile is a comparison made by using the words like or as: "Her hair was as gold as a lion's mane", "His beard was like tiny wires brushing her skin."
When asking a question, it's good to provide as much information as possible. If you can provide the paragraph in question, I can edit the answer to address your specific question.
They are two ratios that express the same relationship between numbers.
