Meaning: 'Markings' refers to the patterns or designs on the surface of something, in this case, the tiger shark's body.

Wrong options:

• transplant: Transplant is a verb meaning to move something from one place to another, which does not fit the context of describing physical features.
• function: Function is a noun that refers to the purpose or role of something, which does not relate to the visual characteristics of the shark.
• feature: Feature is a noun that describes a distinctive attribute, but it does not specifically refer to the patterns on the shark's body as 'markings' does.
• fade: Fade is a verb meaning to gradually disappear, which does not describe the patterns themselves but rather their change over time.
• detection: Detection is a noun that refers to the act of discovering something, which is unrelated to the physical appearance of the shark.

Correct answer: fade

Explanation: The verb 'fade' indicates a gradual loss of visibility or intensity, which is appropriate in the context of the stripes on the tiger shark diminishing as it ages. It fits grammatically as an action that describes what happens to the stripes.

Meaning: 'Fade' means to gradually become less visible or to lose brightness.

Wrong options:

• transplant: Transplant does not fit as it refers to moving something from one place to another, which is unrelated to the process of stripes changing.
• function: Function is a noun that does not convey the action of the stripes changing over time.
• markings: Markings is a noun that describes the patterns but does not indicate any action related to their visibility.
• feature: Feature is a noun that does not describe an action and is not relevant to the fading process.
• detection: Detection is a noun that refers to discovering something, which does not apply to the fading of stripes.

Correct answer: feature

Explanation: The word 'feature' serves as a noun that describes a distinctive characteristic or attribute, which is appropriate in the context of identifying individual tiger sharks. It fits grammatically as it complements the verb 'used.'

Meaning: 'Feature' refers to a distinctive attribute or aspect of something, in this case, the tiger shark's identifying characteristics.

Wrong options:

• transplant: Transplant does not fit as it refers to moving something, which is unrelated to identifying characteristics.
• markings: Markings refers to the patterns but does not convey the idea of a characteristic used for identification.
• fade: Fade is a verb that describes an action, not a noun that can serve as an identifying characteristic.
• detection: Detection is a noun related to discovering something, which does not apply to the context of identifying features.

Correct answer: merge

Explanation: The verb 'merge' indicates the process of combining or blending together, which is suitable in the context of young tiger sharks' blotches becoming stripes. It fits grammatically as an action that describes the transformation of their appearance.

Meaning: 'Merge' means to combine or blend into one, in this case, the blotches on the shark's body becoming stripes.

Wrong options:

• transplant: Transplant does not fit as it refers to moving something from one place to another, which is unrelated to the merging of patterns.
• function: Function is a noun that does not describe an action and is not relevant to the context of physical changes in appearance.
• feature: Feature is a noun that does not convey the action of combining patterns and is not appropriate here.
• fade: Fade describes a loss of visibility, which does not relate to the process of patterns combining into stripes.
• detection: Detection is a noun that refers to discovering something, which does not apply to the merging of patterns.