Meaning: 'Primarily' means 'for the most part' or 'mainly,' indicating that the main purpose of the stripes is to protect zebras from insects.

Wrong options:

• invisibility: 'Invisibility' refers to the state of being unseen, which does not fit the context of protection as it implies a lack of visibility rather than a protective function.
• identity: 'Identity' relates to the characteristics or qualities that define someone or something, which does not connect to the protective role of stripes in this context.
• memory: 'Memory' refers to the ability to remember, which is unrelated to the function of stripes in protecting zebras from insects.

Correct answer: according

Explanation: The word 'according' fits grammatically as it introduces a source or basis for the information that follows. It is contextually appropriate as it references the study that provides evidence for the claim about stripes.

Meaning: 'According' means 'as stated by' or 'in agreement with,' indicating that the information is based on the findings of the study mentioned.

Wrong options:

• distorting: 'Distorting' means to twist or alter the shape of something, which does not fit the context of referencing a study's findings.
• shorting: 'Shorting' is a term often used in finance or electronics, which is irrelevant in this context and does not relate to the study.
• predisposing: 'Predisposing' means to make someone or something more likely to behave in a certain way, which does not fit the context of citing a study.

Correct answer: direction

Explanation: The word 'direction' fits grammatically as a noun that describes the path along which something moves or points. It is contextually relevant as it relates to how the stripes affect the polarized light's reflection.

Meaning: 'Direction' refers to the course along which something moves or points, in this case, how the light is reflected due to the stripes' arrangement.

Wrong options:

• question: 'Question' refers to an inquiry or a problem to be solved, which does not fit the context of discussing light reflection.
• septum: 'Septum' is a term used in anatomy or biology to describe a dividing wall, which is unrelated to the context of light and stripes.
• supervision: 'Supervision' refers to the act of overseeing or managing, which does not relate to the concept of light direction.

Correct answer: zebra-striped

Explanation: The term 'zebra-striped' fits grammatically as an adjective describing the color pattern of the models. It is contextually appropriate as it directly relates to the appearance of zebras and their stripes.

Meaning: 'Zebra-striped' describes something that has stripes similar to those of a zebra, specifically black and white stripes.

Wrong options:

• bombsite: 'Bombsite' refers to a location in a game or military context, which is irrelevant to the discussion of zebra coloration.
• backslide: 'Backslide' means to revert to a previous state, which does not fit the context of describing horse models.
• gunfight: 'Gunfight' refers to a shootout or battle, which is unrelated to the topic of zebra coloration.

Correct answer: avoiding

Explanation: The word 'avoiding' fits grammatically as a gerund that describes the action of steering clear of something. It is contextually relevant as it indicates the purpose of the stripes in relation to horseflies.

Meaning: 'Avoiding' means to keep away from or prevent something from happening, in this case, keeping away from horseflies.

Wrong options:

• spoiling: 'Spoiling' means to ruin or damage, which does not fit the context of protecting zebras from horseflies.
• discoing: 'Discoing' is not a standard verb and does not relate to the context of animal behavior or protection.
• broiling: 'Broiling' refers to cooking with direct heat, which is irrelevant to the context of zebras and horseflies.

Correct answer: attention

Explanation: The word 'attention' fits grammatically as a noun that refers to the act of focusing on something. It is contextually appropriate as it describes what the horseflies are drawn to.

Meaning: 'Attention' refers to the notice taken of someone or something, in this case, the interest that horseflies show towards zebras.

Wrong options:

• welcome: 'Welcome' is a greeting or expression of goodwill, which does not fit the context of horseflies' behavior.
• indigestion: 'Indigestion' refers to digestive discomfort, which is unrelated to the topic of horseflies and zebras.
• kinsman: 'Kinsman' refers to a relative or family member, which does not connect to the context of attention from horseflies.