How light brings about tropic movement in stem and root of a flowering plant

Plants grow towards or away from the light, the type of tropism in the response to light is called phototropism. In general, the stems usually show positive phototropism, while roots show negative phototropism. Leaves also positively respond toward the source of light.

Explanation:

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

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