"You’re as light as a feather." This line is an example of -

♦ Hyperbole:
- অতিরঞ্জন করা।
- An exaggerated statement or an extreme overstatement.
- Hyperbole is a figure of speech that uses an exaggerated or extravagant statement to create a strong, emotional response. As a figure of speech, it is not intended to be taken literally. Hyperbole is frequently used for humor.

- Example:

“I'll love you, dear, I'll love you
Till China and Africa meet,
And the river jumps over the mountain
And the salmon sing in the street," (by W.H. Auden: As I Walk Out One Evening)

• You’re as light as a feather.
- উল্লিখিত লাইনটি একটি Hyperbole এর উদাহরণ, কারণ কারো ওজন feather এর মতো হওয়া সম্ভম নয়, এখানে এটি অতিরঞ্জন করা হয়েছে।

• উল্লেখিত প্রশ্নের বাকি অপশন গুলো হলো: 
- Metaphor: An implicit comparison between two different thing.
- Machinery: The supernatural agents used in an epic or a mock epic.
- Alliteration: It means repetition of a consonant at the beginning.

Source: ABC of English Literature by Dr M Mofizar Rahman