A.I. Explanation:

Correct answer: incur

Explanation: The verb 'incur' is used here to indicate that the food we eat can lead to significant health and environmental costs. It fits grammatically as it is in the present tense, aligning with the ongoing action described in the sentence.

Meaning: 'Incur' means to become subject to something unwelcome or unpleasant as a result of one's own actions, in this case, costs associated with food choices.

Wrong options:

• prove: The verb 'prove' means to demonstrate the truth or existence of something, which does not fit the context of incurring costs.
• degradation: While 'degradation' is relevant to the topic, it is a noun and does not fit grammatically in this verb position.
• variation: 'Variation' is a noun that refers to a change or difference, which does not fit the context of incurring costs.
• shifts: 'Shifts' is a noun that refers to changes, but it does not convey the action of incurring costs.
• conservation: 'Conservation' is a noun that refers to the act of preserving something, which does not fit the context of incurring costs.

Correct answer: degradation

Explanation: The term 'degradation' is a noun that refers to the deterioration of the soil quality, which fits contextually as it is one of the negative consequences of food choices mentioned in the sentence.

Meaning: 'Degradation' means the process of something being damaged or deteriorated, particularly in terms of environmental quality.

Wrong options:

• incur: 'Incur' is a verb and does not fit as a noun in this context.
• variation: 'Variation' is a noun that refers to differences, which does not specifically relate to the deterioration of soil.
• shifts: 'Shifts' is a noun that refers to changes, but it does not relate to the concept of soil quality deterioration.
• conservation: 'Conservation' is a noun that refers to the act of preserving, which does not fit the context of soil deterioration.

Correct answer: shifts

Explanation: The word 'shifts' is a noun that refers to small changes in food choices. It fits grammatically and contextually as it describes the potential adjustments Americans can make to improve health and environmental outcomes.

Meaning: 'Shifts' means changes or alterations, particularly in the context of food choices.

Wrong options:

• incur: 'Incur' is a verb and does not fit as a noun in this context.
• degradation: 'Degradation' is a noun that refers to deterioration, which does not relate to changes in food choices.
• variation: 'Variation' is a noun that refers to differences, but it does not specifically imply the small changes suggested in the context.
• conservation: 'Conservation' is a noun that refers to preservation, which does not fit the context of making changes in food choices.