input question: What is the missing first step of the following process: - The passenger arrives early at the airport - The luggage is checked - The passenger waits in line - The passenger shows their identification and gets a boarding pass - The passenger goes to their gate - The passenger gets in line when it's time to board - The person boards the plane - The plane arrives at the destination - The passenger gets off the plane at their destination.???
output answer: An airline reservation is made

input question: What is the missing first step of the following process: - Food is chewed and mixed with saliva (spit) - Food travels down the esophagus (throat) - Food travels into the stomach - Acid in the stomach breaks the food down further - Food travels into the small intestine - Nutrients from food are absorbed into the blood stream - Food travels into the large intestine - Most of the remaining material is now waste - The waste is eventually removed from the body.???
output answer: Food is put into mouth

input question: What is the missing first step of the following process: - Through erosion, the stream cuts into the soil and bedrock - Through continuous erosion, a deep gash is cut through - After many years the river may dry up - A dry ravine is left -???
output answer: A stream or river must occur

input question: What is the missing first step of the following process: - Engines produce carbon dioxide - Living things produce waste - Waste decomposes - Decomposition produces methane - Water evaporates - Water vapor joins the atmosphere - Carbon dioxide, water vapor and methane are greenhouse gases -???
output answer:
People breathe and expel carbon dioxide