| Front | What resources on earth are limited? |
| Back | The earth's resources of metal ores are limited |
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| Front | What are the first four members of the homogonous series of alcohols? |
| Back | Methanol,Ethanol,Propanol and Butanol |
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| Front | What do sewage and agricultural waste water require? |
| Back | They require removal of organic matter and harmful microbes |
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