Meaning: 'Struggles' means to experience difficulty or to fight against challenges, indicating that the world is having a hard time dealing with climate change.

Wrong options:

• disagrees: 'Disagrees' implies a difference of opinion, which does not fit the context of addressing climate change.
• combines: 'Combines' suggests merging elements, which is not relevant to the struggle against climate change.
• compares: 'Compares' indicates a comparison between two or more items, which does not align with the context of the world's efforts against climate change.

Correct answer: ramping

Explanation: The term 'ramping' is appropriate as it suggests an increase or acceleration, which is necessary for enhancing energy production from fusion reactions. This aligns with the context of needing to boost energy output significantly.

Meaning: 'Ramping' means to increase or accelerate, particularly in terms of production or intensity, indicating the need for a substantial increase in energy output from fusion.

Wrong options:

• declining: 'Declining' means decreasing, which contradicts the need for increased energy production.
• receding: 'Receding' implies moving back or diminishing, which is not suitable in the context of enhancing energy output.
• retaining: 'Retaining' suggests keeping something the same, which does not fit the context of needing to increase energy production.

Correct answer: momentous

Explanation: The word 'momentous' is fitting as it describes efforts that are of great importance or significance, which is necessary for the large-scale implementation of fusion energy. This aligns with the context of the challenges faced in scaling up energy production.

Meaning: 'Momentous' means of great importance or significance, indicating that the efforts required for fusion energy are substantial and impactful.

Wrong options:

• mental: 'Mental' relates to the mind and does not pertain to the physical efforts needed for energy production.
• limited: 'Limited' suggests a lack of scope or significance, which contradicts the idea of significant efforts required.
• futile: 'Futile' implies that efforts would be pointless, which does not align with the context of striving for significant advancements in energy production.

Correct answer: resistant

Explanation: The term 'resistant' is appropriate as it indicates opposition to change, which fits the context of politicians who may not support rapid shifts away from existing fuels and infrastructure. This aligns with the overall theme of challenges in transitioning to new energy sources.

Meaning: 'Resistant' means opposing or being unwilling to accept change, indicating that politicians may be against rapid changes in energy policy.

Wrong options:

• rebellious: 'Rebellious' suggests active resistance against authority, which does not fit the context of political support for existing systems.
• hospitable: 'Hospitable' implies welcoming or accommodating, which contradicts the idea of resistance to change.
• receptive: 'Receptive' means open to new ideas, which is the opposite of being resistant.

Correct answer: dependence

Explanation: The word 'dependence' fits grammatically and contextually as it refers to reliance on fossil fuels, which is the issue being addressed in the context of seeking alternatives. It highlights the need to reduce reliance on non-renewable energy sources.

Meaning: 'Dependence' means reliance on something, indicating that the goal is to lessen the reliance on fossil fuels for energy.

Wrong options:

• comments: 'Comments' refers to remarks or statements, which does not fit the context of energy reliance.
• research: 'Research' pertains to investigation or study, which is not relevant to the concept of reliance on fossil fuels.
• influence: 'Influence' refers to the capacity to have an effect on something, which does not directly relate to the idea of reliance on fossil fuels.