Meaning: 'Answer' refers to a response or solution to a question or problem, in this case, how chimpanzees learn to use tools.

Wrong options:

• plan: The word 'plan' is a noun that refers to a strategy or scheme, which does not fit the context of seeking knowledge about behavior.
• sent: The word 'sent' is a verb that does not fit grammatically as it does not relate to the act of seeking knowledge.
• applied: The word 'applied' is a verb that does not fit the context of what researchers are seeking in their studies.
• due: The word 'due' is an adjective that indicates something expected or owed, which does not fit the context of seeking an answer.
• without: The word 'without' is a preposition that does not fit grammatically as it does not relate to the act of seeking knowledge.
• despite: The word 'despite' is a preposition that indicates contrast, which does not fit the context of seeking an answer.

Correct answer: applied

Explanation: The term 'applied' is an adjective that describes how findings are utilized in understanding primate cognition. It fits grammatically and contextually, indicating that the findings have practical implications.

Meaning: 'Applied' refers to something that is put into practice or used in a practical context, in this case, findings related to primate cognition.

Wrong options:

• plan: The word 'plan' does not fit as it refers to a strategy rather than how findings are utilized.
• sent: The word 'sent' is a verb that does not fit grammatically in this context.
• answer: The word 'answer' is a noun that does not describe the application of findings.
• due: The word 'due' does not fit as it indicates expectation rather than application.
• without: The word 'without' is a preposition that does not relate to the application of findings.
• despite: The word 'despite' is a preposition indicating contrast, which does not fit the context of applying findings.

Correct answer: sent

Explanation: The word 'sent' is the past tense of the verb 'send,' which fits grammatically as it describes the action taken during the experiment. It aligns with the context of testing communication skills.

Meaning: 'Sent' refers to the action of dispatching signals, indicating that signals were communicated to test skills.

Wrong options:

• plan: The word 'plan' does not fit as it is a noun and does not describe an action taken in the experiment.
• applied: The word 'applied' is a verb that does not fit in the context of describing the action of sending signals.
• answer: The word 'answer' is a noun that does not describe an action related to the experiment.
• due: The word 'due' does not fit as it does not relate to the action of sending signals.
• without: The word 'without' is a preposition that does not describe an action taken in the experiment.
• despite: The word 'despite' is a preposition that indicates contrast, which does not fit the context of sending signals.

Correct answer: without

Explanation: The word 'without' is a preposition that indicates the absence of something, fitting grammatically and contextually as it describes the condition under which responses occurred.

Meaning: 'Without' means in the absence of, indicating that responses happened without any prior training.

Wrong options:

• plan: The word 'plan' does not fit as it is a noun and does not describe a condition of occurrence.
• sent: The word 'sent' is a verb that does not fit grammatically in this context.
• answer: The word 'answer' is a noun that does not describe a condition related to the occurrence of responses.
• applied: The word 'applied' is a verb that does not fit in the context of describing the condition of responses.
• due: The word 'due' does not fit as it indicates expectation rather than absence.
• despite: The word 'despite' is a preposition indicating contrast, which does not fit the context of responses occurring.