Meaning: 'In' indicates a state or condition, suggesting that the developments have led to the climate crisis.

Wrong options:

• by: 'By' indicates the means or agent of an action, which does not fit here as it does not convey the outcome of the developments.
• to: 'To' suggests direction or purpose, which is not appropriate in this context as it does not indicate a result.
• on: 'On' typically indicates a surface or a topic, and does not convey the causative relationship needed in this sentence.

Correct answer: have not been met

Explanation: The phrase 'have not been met' is in the present perfect tense, which is appropriate here as it indicates that the standards are still not met up to the present time. This aligns with the ongoing nature of the issue being discussed.

Meaning: 'Have not been met' means that the required standards for sustainability have not been achieved or fulfilled.

Wrong options:

• had not been met: 'Had not been met' is past perfect tense, suggesting a completed action in the past, which does not fit the current context of ongoing standards.
• has not been met: 'Has not been met' is singular and does not agree with the plural subject 'standards,' making it grammatically incorrect.
• were not being met: 'Were not being met' implies a past continuous action, which does not convey the current relevance of the standards.

Correct answer: However

Explanation: The word 'However' serves as a discourse marker that introduces a contrast to the previous statement about solar energy being a solution. It fits grammatically and contextually as it signals a shift in the argument.

Meaning: 'However' means 'nevertheless' or 'but,' indicating that despite the benefits of solar energy, there are opposing views.

Wrong options:

• Although: 'Although' introduces a subordinate clause and does not fit the structure of the sentence as it would require a different grammatical construction.
• Even though: Similar to 'Although,' 'Even though' is used for subordinate clauses and does not fit the main clause structure here.
• In contrast: 'In contrast' suggests a direct comparison between two different ideas, which does not fit as smoothly as 'However' in this context.

Correct answer: address

Explanation: The verb 'address' is appropriate here as it means to deal with or tackle an issue, fitting grammatically and contextually in the sentence about resolving the claims against solar panels.

Meaning: 'Address' means to focus on or deal with a problem or issue.

Wrong options:

• process: 'Process' refers to a series of actions or steps taken to achieve a particular end, which does not fit the context of resolving issues directly.
• action: 'Action' is a noun that does not fit grammatically in the sentence where a verb is required to indicate what needs to be done about the issues.
• amend: 'Amend' means to make changes or corrections, which is not as direct as 'address' in the context of dealing with the issues at hand.