Explanation:

The relationship between the words "chatter" and "talk" is that they are synonyms or words that have similar meanings. Similarly, the relationship between the words "flutter" and "flap" is also that they are synonyms.

Chatter:
- Chatter refers to the sound made by a person or animal when they talk rapidly or in a lively manner.
- It can also refer to a series of quick, high-pitched sounds made by objects such as machinery or bird calls.

Talk:
- Talk is a verb that means to communicate or exchange information by speaking.
- It can also refer to a conversation or discussion.

The relationship between "chatter" and "talk" is that they both refer to communication or exchanging information through sound. Therefore, the correct answer is option 'D' - flap.

Flutter:
- Flutter is a verb that means to fly or move quickly and lightly, typically with a series of rapid movements.
- It can also refer to a feeling of excitement or nervousness.

Flap:
- Flap is a verb that means to move up and down or back and forth with a waving or vibrating motion.
- It can also refer to a flat piece of material that is attached at one edge and is free to move, such as the wings of a bird or the cover of a book.

The relationship between "flutter" and "flap" is that they both refer to a rapid, back-and-forth movement. Therefore, the correct answer is option 'D' - flap.