The basic idea, no matter how it is presented conveys a simple concept about the paragraph.
In this paragraph, the main idea is presented as an exercise:
Walking is a difficult and safe <u>exercise</u> for beginners. Walking is an easy and safe <u>exercise</u> for beginners. Walking is a boring and dangerous form of <u>exercise</u>. Walking is an exciting and very effective form of <u>exercise</u>
Note the words in bold and underlined. No matter whether exercise is safe or not, the matter is that the walking is an exercise.
The movie isn't exactly like the myth. In myth, Perseus uses his magical sword to slay the sea beast. This is also the same sword he had used to slay Medusa.
The correct answer is phrase. A phrase is a group of words that work together to express an idea and can function as a noun, adjective, verb, or adverb.
