Scientists were exploring a new cave ____ they found ancient drawings. Inventors were working in the lab ____ their assistant was taking notes. People waited ____ hours to see the new discovery in the museum. Explorers were climbing the mountain ____ they saw a rare bird. Scientists were studying the plants ____ it was raining. People stayed in the library ____ a long time to read about discoveries. Inventors were testing a new machine ____ it suddenly stopped. Explorers were walking in the desert ____ the sun was very hot.

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