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New transportation systems ______ in major cities to reduce traffic congestion.

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The city mayor ______ the locals to pick up trash on the beach.

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The project has been carried out to ______ the healthcare system in order to care for more sick people.

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The locals have suffered from water pollution for 3 years, so they need a ______.

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The city council got a group of volunteers ______ up the slums to improve living conditions.

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Over 100 trash cans ______ in public areas to deal with littering.

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When an area becomes overcrowded, it can lead to a rise in ______ and create problems with security and housing.

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The population density ______ by 3% because lots of people have left for the cities.