Meaning: 'Grains' refers to small, individual particles, in this case, of sand.

Wrong options:

• summit: 'Summit' is a noun that refers to the highest point of something, which does not relate to sand and is not appropriate in this context.
• rich: 'Rich' is an adjective that describes abundance or wealth, which does not fit as a noun for sand particles.
• fertile: 'Fertile' is an adjective that describes land capable of supporting plant growth, which does not fit as a noun here.
• clouds: 'Clouds' are collections of water vapor in the sky, which are unrelated to the context of sand and do not fit grammatically.
• planting: 'Planting' is a gerund that refers to the act of putting plants in the ground, which does not fit as a noun for sand particles.

Correct answer: fertile

Explanation: The term 'fertile' is an adjective that describes land capable of producing abundant vegetation. It fits contextually as it contrasts with the transformation into desert, highlighting the impact of drifting sands.

Meaning: 'Fertile' refers to land that is rich in nutrients and capable of supporting plant growth.

Wrong options:

• grains: 'Grains' is a plural noun referring to small particles, which does not fit as a descriptor for land.
• rich: 'Rich' is an adjective that can describe land but is less specific than 'fertile' in this context.
• surface: 'Surface' is a noun that refers to the outermost layer, which does not describe the quality of land.
• nourishment: 'Nourishment' is a noun that refers to food or sustenance, which does not fit as a descriptor for land.

Correct answer: planting

Explanation: The word 'planting' is a gerund that refers to the act of putting plants in the ground. It fits grammatically and contextually as it describes the action taken to stabilize dunes.

Meaning: 'Planting' refers to the act of placing seeds or plants in the soil for growth.

Wrong options:

• summit: 'Summit' is a noun that refers to the highest point, which does not relate to the action of stabilizing dunes.
• grains: 'Grains' is a noun that refers to small particles, which does not fit as an action.
• rich: 'Rich' is an adjective that does not describe an action and is not appropriate in this context.
• fertile: 'Fertile' is an adjective that describes land quality, which does not fit as an action.

Correct answer: nourishment

Explanation: The term 'nourishment' is a noun that refers to food or sustenance necessary for growth. It fits contextually as it describes what the grass can find even in sand, emphasizing its resilience.

Meaning: 'Nourishment' refers to the substances necessary for growth and health, particularly for plants.

Wrong options:

• summit: 'Summit' is a noun that refers to the highest point, which does not relate to what the grass seeks in sand.
• grains: 'Grains' is a noun that refers to small particles, which does not fit as a source of sustenance.
• rich: 'Rich' is an adjective that describes abundance, which does not fit as a noun for what the grass seeks.
• planting: 'Planting' is a gerund that refers to the act of putting plants in the ground, which does not fit as a source of sustenance.

Correct answer: surface

Explanation: The word 'surface' is a noun that refers to the outermost layer of something. It fits grammatically and contextually as it describes the area of the dune that the grass spreads over, maintaining coherence in the sentence.

Meaning: 'Surface' refers to the outer layer or top part of something, in this case, the dune.

Wrong options:

• summit: 'Summit' is a noun that refers to the highest point, which does not fit as it does not describe the area of the dune.
• grains: 'Grains' is a noun that refers to small particles, which does not fit as a descriptor for the dune's area.
• rich: 'Rich' is an adjective that does not fit as a noun for describing the dune's area.
• fertile: 'Fertile' is an adjective that describes land quality, which does not fit as a noun for the dune's area.