4. In understanding forces, what may have caused the falling of leaves of a tree?
A. The withering of leaves causes them to fall.
B. The blowing of wind causes the leaves to fall.
C. The rain pouring heavily causes the leaves to fall.
D. The gravitational pull of the earth causes the fall of leaves on the tree.
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Explanation:
According to Peter Raven, president of the Missouri Botanical Garden and a renowned botanist, the wind doesn't gently pull leaves off trees.
Trees in temperate and boreal zones face punishingly cold temperatures and frigid winds, conditions that would damage leaves, so trees have to reduce themselves to their toughest parts—stems, trunks, branches, bark. Leaves must fall.
Due to inertia of rest, the leaves try to be in rest when a tree is shaken. But the branch and trunk comes into motion which causes the leaves to separate from its branch. Hence, the leaves fall when a tree is shaken.
So the answer is A. The Withering of leaves causes them to fall.