When Diatoms Die,their Shells Fall to the Floor of the Ocean

question 13

Multiple Choice

When diatoms die,their shells fall to the floor of the ocean or lake that they inhabit and form sediments called diatomaceous earth (DE) .Diatoms can be identified by their shells,and different species of diatoms prefer different water temperatures.The diatoms' porous shells are hard but often break and result in sharp edges.Crop farmers incorporate DE into their soil to help kill insect pests.When insects encounter DE,sharp shell edges cut through their exoskeletons and then softer,broken down DE absorbs insect body fluids,thereby causing the insects to die due to dehydration.Why might farmers who raise large livestock also use DE in the animals' feed?

• A)The sharp shells can damage the tissue of intestinal parasites and eventually kill them.
• B)DE helps to slow down the livestock's digestion of food,thereby increasing nutrient absorption.
• C)The porous nature of the shells in the DE helps keep livestock hydrated.
• D)DE encourages growth of "healthy" intestinal bacteria.

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