Meaning: An 'achievement' refers to something that has been accomplished successfully, especially through effort or skill.

Wrong options:

• compassion: 'Compassion' is a noun that refers to sympathetic pity and concern for the sufferings or misfortunes of others, which does not relate to the context of scientific discovery.
• pushed: 'Pushed' is a verb that implies forceful movement or encouragement, which does not fit as a noun in this context.
• equipment: While 'equipment' is a noun, it does not describe the nature of the discovery itself but rather the tools used, making it contextually inappropriate here.
• sophistication: 'Sophistication' refers to the quality of being sophisticated or complex, which does not directly describe the discovery as a significant accomplishment.
• set: 'Set' is a verb that indicates the action of placing something in a specified position, which does not fit grammatically as a noun in this context.
• hit: 'Hit' is a verb that indicates achieving something, but it does not serve as a noun to describe the discovery.

Correct answer: equipment

Explanation: The term 'equipment' is a noun that refers to the tools and instruments necessary for conducting scientific research. It fits grammatically and contextually as it describes what the astrophysicists used in their work.

Meaning: 'Equipment' refers to the necessary items or tools used for a specific purpose, especially in scientific contexts.

Wrong options:

• compassion: 'Compassion' is a noun that refers to a feeling of sympathy, which does not relate to the tools used in scientific research.
• pushed: 'Pushed' is a verb that does not fit as it does not describe tools or instruments.
• set: 'Set' is a verb that indicates an action and does not refer to tools or equipment.
• hit: 'Hit' is a verb that indicates achieving something, which does not fit as a noun describing tools.
• achievement: While 'achievement' is a noun, it describes a success rather than the tools used to achieve it, making it contextually inappropriate here.
• sophistication: 'Sophistication' refers to complexity or refinement, which does not describe the tools used in the research.

Correct answer: set

Explanation: The word 'set' is used as a verb here, indicating the action of beginning or embarking on a mission. It fits grammatically and contextually as it describes the astrophysicists' initiative to capture gravitational waves.

Meaning: 'Set out' means to begin a journey or task with a specific goal in mind.

Wrong options:

• compassion: 'Compassion' is a noun that does not relate to the action of embarking on a scientific mission.
• pushed: 'Pushed' is a verb that implies forceful action, which does not fit the context of initiating a scientific endeavor.
• equipment: 'Equipment' is a noun that refers to tools, which does not fit grammatically as an action in this context.
• hit: 'Hit' is a verb that indicates achieving something, but it does not describe the action of starting a mission.
• achievement: 'Achievement' is a noun that describes a success, which does not fit as an action in this context.
• sophistication: 'Sophistication' is a noun that refers to complexity, which does not describe the action of embarking on a task.

Correct answer: hit

Explanation: The word 'hit' is used as a verb that indicates achieving a significant success or breakthrough. It fits grammatically and contextually as it describes the moment of confirming the discovery of gravitational waves.

Meaning: 'Hit' in this context means to achieve or reach a significant milestone or success.

Wrong options:

• compassion: 'Compassion' is a noun that refers to a feeling of sympathy, which does not relate to achieving a scientific breakthrough.
• pushed: 'Pushed' is a verb that implies forceful action, which does not fit the context of confirming a discovery.
• equipment: 'Equipment' is a noun that refers to tools, which does not fit grammatically as an action in this context.
• set: 'Set' is a verb that indicates starting an action, but it does not convey the achievement of confirming a discovery.
• achievement: While 'achievement' is a noun that describes a success, it does not fit as a verb indicating the action of confirming the discovery.
• sophistication: 'Sophistication' is a noun that refers to complexity, which does not describe the action of achieving a breakthrough.