Meaning: 'In the past' refers to a time that has already occurred, indicating that the exploitation happened before now.

Wrong options:

• in the present: 'In the present' refers to the current time, which contradicts the context of discussing past damages to the ecosystem.
• while: 'While' is a conjunction used to indicate simultaneous actions, which does not fit as it does not provide a temporal reference for past actions.
• Therefore: 'Therefore' is a conjunctive adverb that indicates a conclusion, which does not fit the context of describing past exploitation.
• And: 'And' is a coordinating conjunction that connects ideas but does not provide a temporal context, making it unsuitable here.
• Because: 'Because' is a conjunction that introduces a reason, which does not fit as it does not indicate a time frame.
• have already been: 'Have already been' is a verb phrase that indicates a completed action, but it does not relate to the past exploitation context.

Correct answer: while

Explanation: The word 'while' serves as a conjunction that introduces a contrast between two simultaneous actions: developing the region and caring for the environment. This fits grammatically and contextually, as it highlights the balance between development and conservation.

Meaning: 'While' indicates that two actions are happening at the same time, suggesting a contrast or balance between them.

Wrong options:

• in the present: 'In the present' does not function as a conjunction and fails to connect the two actions appropriately.
• in the past: 'In the past' does not fit as it does not indicate simultaneous actions and is not a conjunction.
• Therefore: 'Therefore' does not serve as a conjunction to connect the two actions and implies a conclusion rather than a simultaneous occurrence.
• And: 'And' connects ideas but does not imply contrast, making it less suitable for indicating the relationship between development and care.
• Because: 'Because' introduces a reason rather than a simultaneous action, which does not fit the context of the sentence.
• have already been: 'Have already been' is a verb phrase that does not function as a conjunction and does not connect the two actions.

Correct answer: Because

Explanation: The word 'Because' introduces a causal relationship, explaining why the Antarctic remains largely undamaged. This fits grammatically as it provides a reason for the statement that follows.

Meaning: 'Because' is used to introduce a reason or explanation for something.

Wrong options:

• in the present: 'In the present' does not provide a causal relationship and is not relevant to the context of explaining the state of the Antarctic.
• in the past: 'In the past' does not fit as it does not introduce a reason or explanation for the current state of the Antarctic.
• while: 'While' indicates simultaneous actions but does not provide a reason, making it unsuitable for this context.
• Therefore: 'Therefore' indicates a conclusion rather than a reason, which does not fit the context of explaining the Antarctic's condition.
• And: 'And' connects ideas but does not provide a causal relationship, making it inappropriate here.
• have already been: 'Have already been' is a verb phrase that does not function as a conjunction and does not introduce a reason.

Correct answer: have already been

Explanation: The phrase 'have already been' indicates a completed action in the present perfect tense, which is appropriate for discussing discoveries that have occurred up to the present time. This fits grammatically and contextually as it highlights the ongoing relevance of the ozone layer issue.

Meaning: 'Have already been' indicates that something has occurred at some point before now, emphasizing its relevance to the present.

Wrong options:

• in the present: 'In the present' does not fit grammatically as it does not indicate an action that has been completed.
• in the past: 'In the past' suggests a completed action but does not convey the ongoing relevance of the discoveries made about the ozone layer.
• while: 'While' does not function as a verb phrase and does not indicate a completed action, making it unsuitable here.
• Therefore: 'Therefore' does not indicate an action and is not relevant to the context of discoveries.
• And: 'And' does not indicate an action and fails to convey the necessary meaning in this context.
• Because: 'Because' does not function as a verb phrase and does not indicate a completed action.