Meaning: 'Does' is a form of the verb 'do,' used here to indicate that the technique operates independently of the animal's cooperation.

Wrong options:

• can: The word 'can' suggests ability but does not fit the context of a technique that is being described as not requiring cooperation.
• must: 'Must' implies obligation or necessity, which does not align with the context of describing a technique that operates independently.
• shall: 'Shall' is used to indicate future action or intention, which is not appropriate in this present tense context.

Correct answer: across

Explanation: The word 'across' is the correct choice as it indicates comparison between different species. It fits grammatically and contextually, as it suggests a broad comparison rather than a limited or specific one.

Meaning: 'Across' means from one side to the other or in relation to various entities, in this case, different species.

Wrong options:

• Over: The word 'over' typically indicates a position above something and does not convey the idea of comparison between species.
• with: 'With' suggests a connection or association but does not imply the act of comparing across different groups.
• in: The word 'in' indicates a location or state, which does not fit the context of comparing species.

Correct answer: Instead

Explanation: The word 'Instead' is appropriate here as it introduces an alternative approach to the previous statement about comparing brain sizes. It fits logically and contextually, indicating a shift in focus to the Cephalization index.

Meaning: 'Instead' means in place of something else, suggesting that the Cephalization index is used as an alternative method for comparison.

Wrong options:

• Moreover: 'Moreover' adds information but does not indicate a shift in focus, which is necessary in this context.
• However: 'However' introduces a contrast but does not fit the context of presenting an alternative method.
• Actually: 'Actually' implies a correction or clarification, which does not align with the intended meaning of presenting an alternative.

Correct answer: followed

Explanation: The word 'followed' is the correct choice as it is the past participle form used here to indicate that humans are succeeded by other intelligent species. It fits grammatically and contextually in the sentence structure.

Meaning: 'Followed' means to come after in order or sequence, indicating that great apes, porpoises, and elephants come after humans in intelligence ranking.

Wrong options:

• follows: 'Follows' is present tense and does not fit the past context of the sentence, which discusses the ranking of intelligence.
• follow: 'Follow' is the base form of the verb and does not agree with the subject in this context.
• following: 'Following' is a gerund or participle that does not fit the grammatical structure required here.

Correct answer: rule

Explanation: The word 'rule' is the correct choice as it indicates a general principle or guideline regarding intelligence in animals. It fits grammatically and contextually within the sentence.

Meaning: 'Rule' refers to a general principle or guideline that is commonly accepted, in this case, regarding the intelligence of animals based on their dietary habits.

Wrong options:

• theory: 'Theory' suggests a system of ideas intended to explain something, which does not fit the context of a general guideline.
• way: The word 'way' is too vague and does not convey the authoritative sense of a guideline or principle.
• model: 'Model' implies a representation or example, which does not align with the context of stating a general rule.