Meaning: 'On' indicates a relationship of influence or effect, suggesting that climate change has an impact on deep ocean life.

Wrong options:

• in: The preposition 'in' suggests being inside or within something, which does not convey the intended meaning of influence in this context.
• of: The preposition 'of' indicates possession or belonging, which does not fit the context of discussing the impact of climate change.
• off: The preposition 'off' typically indicates separation or distance, which is not appropriate when discussing the effects of climate change.

Correct answer: published

Explanation: The verb 'published' is in the past tense, which is appropriate here as it refers to a completed action that has occurred in the past, aligning with the overall past narrative of the study.

Meaning: 'Published' means that the study has been made publicly available in a journal, indicating that the research findings are now accessible to others.

Wrong options:

• publishing: The gerund 'publishing' does not fit grammatically as it suggests an ongoing action rather than a completed one.
• has published: The present perfect 'has published' implies a connection to the present, which is not suitable in this context where the past tense is required.
• be publishing: The phrase 'be publishing' suggests a future or ongoing action, which does not align with the context of a completed study.

Correct answer: previously

Explanation: The adverb 'previously' indicates that the unknown status of the cause existed before the current findings, fitting grammatically and contextually as it refers to a time frame relevant to the study's results.

Meaning: 'Previously' means at an earlier time, indicating that the cause was not known before the current research was conducted.

Wrong options:

• occasionally: The adverb 'occasionally' suggests something happens from time to time, which does not fit the context of something being unknown before the study.
• necessarily: The adverb 'necessarily' implies a requirement or inevitability, which does not apply to the context of knowledge about the cause.
• currently: The adverb 'currently' refers to the present time, which contradicts the idea that the cause was unknown before the study.

Correct answer: causes

Explanation: The noun 'causes' is plural and fits grammatically as it refers to multiple potential reasons for the mass extinction, aligning with the context of scientific investigation.

Meaning: 'Causes' refers to the reasons or factors that lead to an event, in this case, the mass extinction of marine organisms.

Wrong options:

• consequences: The noun 'consequences' refers to the results of an action, which does not fit as the focus is on identifying reasons rather than outcomes.
• elements: The noun 'elements' suggests components or parts, which is too vague and does not specifically refer to reasons for the extinction.
• factors: The noun 'factors' is similar but less precise than 'causes' in this context, as it does not directly imply reasons for the extinction.

Correct answer: Instead

Explanation: The adverb 'Instead' is used to introduce a contrasting idea, indicating that the findings were different from what might have been expected, fitting well grammatically and contextually within the sentence.

Meaning: 'Instead' means in place of or as an alternative, suggesting that the discovered cause was not what was initially considered.

Wrong options:

• However: The adverb 'However' introduces a contrast but does not fit as smoothly in this context where a direct alternative is being presented.
• Thus: The adverb 'Thus' implies a conclusion or result, which does not align with the contrasting nature of the findings being presented.
• So: The adverb 'So' indicates a consequence, which does not fit the context of presenting an alternative explanation.