Meaning: 'Driving' refers to something that propels or motivates action, in this case, scientific progress.

Wrong options:

• ethical: 'Ethical' is an adjective that describes moral principles, which does not fit as it does not describe a force.
• security: 'Security' is a noun that refers to safety or protection, which does not convey the idea of motivation in this context.
• founding: 'Founding' is a gerund that refers to the act of establishing something, which does not fit as a force behind breakthroughs.
• engaged: 'Engaged' is an adjective that describes involvement, which does not fit as a force or motivation.
• afraid: 'Afraid' is an adjective that describes fear, which does not relate to the concept of a driving force.

Correct answer: engaged

Explanation: The term 'engaged' is an adjective that describes a state of being involved or actively participating. It fits grammatically as it describes the subject 'you' and aligns contextually with the idea of curiosity enhancing interaction with the environment.

Meaning: 'Engaged' means being involved or actively participating in something.

Wrong options:

• comfort: 'Comfort' is a noun that refers to a state of physical ease, which does not fit in the context of describing a state of involvement.
• driving: 'Driving' is a gerund that describes motivation, which does not fit as a descriptor for a state of being.
• ethical: 'Ethical' is an adjective that relates to moral principles, which does not describe a state of involvement.
• security: 'Security' is a noun that refers to safety, which does not fit in the context of being involved with surroundings.
• afraid: 'Afraid' is an adjective that describes fear, which does not relate to being actively involved.

Correct answer: afraid

Explanation: The word 'afraid' is an adjective that describes a feeling of fear or apprehension. It fits grammatically as it describes the subject 'you' and contextually aligns with the encouragement to challenge oneself without fear.

Meaning: 'Afraid' means feeling fear or anxiety about something.

Wrong options:

• comfort: 'Comfort' is a noun that refers to a state of ease, which does not fit as it does not describe a feeling of fear.
• driving: 'Driving' is a gerund that refers to motivation, which does not fit in the context of fear or apprehension.
• engaged: 'Engaged' is an adjective that describes involvement, which does not relate to the concept of fear.
• ethical: 'Ethical' is an adjective that pertains to moral principles, which does not describe a feeling of fear.
• security: 'Security' is a noun that refers to safety, which does not fit in the context of fear.

Correct answer: comfort

Explanation: The term 'comfort' is a noun that refers to a state of physical or emotional ease. It fits grammatically as it serves as the object of the preposition 'out of' and contextually aligns with the idea of stepping beyond familiar boundaries.

Meaning: 'Comfort' refers to a state of physical or emotional ease and contentment.

Wrong options:

• driving: 'Driving' is a gerund that refers to motivation, which does not fit as a noun describing a state of ease.
• engaged: 'Engaged' is an adjective that describes involvement, which does not fit as a noun in this context.
• afraid: 'Afraid' is an adjective that describes fear, which does not relate to a state of ease or comfort.
• ethical: 'Ethical' is an adjective that pertains to moral principles, which does not fit as a noun describing a state of being.
• security: 'Security' is a noun that refers to safety, which does not fit in the context of describing a state of ease.