Meaning: 'Commonly' means 'usually' or 'frequently,' suggesting that the term Aboriginal Australians is widely used to describe Native Australians.

Wrong options:

• especially: 'Especially' implies a particular emphasis or significance, which does not fit the general context of how Native Australians are referred to.
• accordingly: 'Accordingly' suggests a consequence or result, which does not align with the intended meaning of how they are referred to.
• completely: 'Completely' indicates totality, which does not apply here as it does not convey the frequency of the term's usage.

Correct answer: Before

Explanation: The word 'Before' appropriately indicates a time frame, establishing that the events described occurred prior to European settlement. This fits grammatically and contextually, as it sets the historical context for the following information about Aboriginal Australians.

Meaning: 'Before' means 'prior to' or 'earlier than,' indicating that the Aboriginal Australians lived as hunter-gatherers in the time leading up to European settlement.

Wrong options:

• Although: 'Although' introduces a contrast, which does not fit the chronological context needed in this sentence.
• Before: This option is the correct answer, so it does not need an explanation.
• Rather than: 'Rather than' suggests a choice between alternatives, which is not applicable in this context as it does not indicate a time relationship.
• Through: 'Through' implies a process or means, which does not convey the necessary temporal relationship.

Correct answer: structure

Explanation: The word 'structure' fits grammatically as a noun that describes the organization or arrangement of the social system of Aboriginal Australians. Contextually, it aligns with the discussion of their complex social systems and beliefs, making it the most suitable choice.

Meaning: 'Structure' refers to the arrangement or organization of something, in this case, the social system of Aboriginal Australians, which is complex and well-defined.

Wrong options:

• facade: 'Facade' refers to a superficial appearance, which does not accurately represent the depth of Aboriginal social systems.
• concept: 'Concept' implies an abstract idea, which does not convey the tangible organization of their social systems.
• appearance: 'Appearance' refers to how something looks, which does not relate to the organizational aspect of their social systems.

Correct answer: preserved

Explanation: The word 'preserved' fits grammatically as a verb indicating that Aboriginal Australians have maintained their cultural practices despite external pressures. Contextually, it aligns with the sentence's focus on their resilience and ongoing contributions to society.

Meaning: 'Preserved' means to maintain or keep something in its original state, indicating that Aboriginal Australians have successfully kept their cultural practices alive.

Wrong options:

• contacted: 'Contacted' implies reaching out or communicating, which does not fit the context of maintaining cultural practices.
• submitted: 'Submitted' suggests yielding or giving in, which contradicts the idea of actively maintaining cultural practices.
• plotted: 'Plotted' implies planning or scheming, which does not relate to the preservation of cultural practices.