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| Mark can still be awarded if one end bond is missing. Allow dot or ~ to represent end bond. Ignore the omission of one H atom provided the bond is shown or one carbon to hydrogen bond missing provided the hydrogen is shown. Zero marks awarded if both end bonds are missing less than or more than three monomers shown a bond between two carbons is missing. |
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| 4. | Between 1960 and 2000 production of plastics increased. |
