Define marginal utility.
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Which of the following structures is not found in both plant and animal cells? a) chloroplast b) cytoskeleton c) ribosomes d) mitochondria

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

For a comparative or experimental investigation, scientists often make a testable about a scientific question, and then they test it in the investigation. a.control b.hypothesis c.procedure d.system