Meaning: 'Revolutionary' means causing a complete or dramatic change, particularly in ideas or practices.

Wrong options:

• abrupt: 'Abrupt' suggests a sudden change, which does not capture the profound and ongoing impact of Darwin's theory on philosophical thought.
• procedural: 'Procedural' refers to a method or process, which does not convey the transformative nature of the changes brought about by the theory.
• systematic: 'Systematic' implies an organized method, but it lacks the connotation of significant change that 'revolutionary' provides.

Correct answer: theories

Explanation: The word 'theories' is the most suitable choice as it refers to established ideas that were discarded in favor of new interpretations, fitting well with the context of anthropologists changing their views.

Meaning: 'Theories' are systematic explanations of phenomena, often based on principles and evidence, which in this case were replaced by new insights.

Wrong options:

• practices: 'Practices' refer to habitual actions or methods, which does not align with the context of changing foundational ideas.
• assumptions: 'Assumptions' are beliefs taken for granted, but they do not specifically denote the structured ideas that were replaced.
• values: 'Values' refer to principles or standards of behavior, which do not directly relate to the scientific ideas being scrapped.

Correct answer: evolution

Explanation: The term 'evolution' is the most appropriate choice as it directly relates to the history of life on earth, emphasizing the process of change over time, which is the main focus of the sentence.

Meaning: 'Evolution' refers to the gradual development of organisms and life forms over time through processes such as natural selection.

Wrong options:

• man: This option is repeated and similarly incorrect for the same reasons as above.
• ocean: 'Ocean' does not relate to the historical process of life but rather refers to a physical environment.

Correct answer: originated

Explanation: The word 'originated' fits well as it indicates the beginning or starting point of life, aligning with the context of the sentence that discusses the emergence of life.

Meaning: 'Originated' means to have begun or started from a particular source or place.

Wrong options:

• started: 'Started' is a more informal term and does not convey the same depth of meaning as 'originated' in this scientific context.
• developed: 'Developed' implies a process of growth or evolution, which is not as precise as 'originated' when discussing the initial emergence of life.
• shaped: 'Shaped' suggests a process of forming or influencing, which does not accurately describe the initial emergence of life.

Correct answer: protection

Explanation: The term 'protection' is the most fitting choice as it describes the primary function of shells in safeguarding mollusks from predators, aligning with the context of the sentence.

Meaning: 'Protection' refers to the act of keeping someone or something safe from harm or danger.

Wrong options:

• attraction: 'Attraction' implies drawing something closer, which does not relate to the defensive purpose of shells.
• distance: 'Distance' refers to the space between objects, which is irrelevant to the function of shells.
• separation: 'Separation' suggests dividing or keeping apart, which does not accurately describe the protective role of shells.

Correct answer: retreats

Explanation: The word 'retreats' is appropriate as it conveys the idea of withdrawing from danger, which aligns with how animals use their shells for safety.

Meaning: 'Retreats' means to withdraw or move back from a position of danger.

Wrong options:

• disguise: 'Disguise' implies hiding one's identity, which does not fit the context of using shells for safety.
• converse: 'Converse' means to engage in conversation, which is unrelated to the protective function of shells.
• offence: 'Offence' refers to an act of aggression, which contradicts the idea of retreating from danger.