Question

what was the significance of collisions of dust, rock, and ice during earths formation?
to modify the density of materials present on earth
to facilitate heat absorption from the surrounding space
to blow away a strong burst of particles from the first atmosphere
to harden materials to form different parts of earths layers

Explanation:

During Earth's formation, collisions of dust, rock, and ice caused materials to compact and heat - up, hardening them to form different parts of Earth's layers. This process was crucial in the differentiation of Earth's interior.

Answer:

to harden materials to form different parts of Earth's layers