The Anwer is c. Dying in equal

Why do plants need nitrate ions?

For making amino acids ( Option A )

The plants need nitrate ions for <u>making amino acids</u>
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The possible number of main effect is THREE.
Main effects refers to the major conditions that are specify in the experiment; these are: room temperature, noise level and room colour. These three factors are manipulated in the designed experiment.
A pig needs food, water, and shelter. Like humans:)