input question: What is the missing first step of the following process: - The oxygen passes through the bronchial tubes to the lungs - The oxygen is moved into the bloodstream - Circulates through the body - The cells in the body exchange the oxygen with carbon dioxide - The bloodstream carries the carbon dioxide back to the lungs - The lungs expel the carbon dioxide through the nose and mouth.???
output answer: A person breathes in oxygen

input question: What is the missing first step of the following process: - Two types of proteins exist in filaments in the muscles - The filaments move when the brain instructs them to - The motion of the filaments cause the muscle to shorten and contract - Opposing pairs of muscles exist in order to provide the necessary range of motion.???
output answer: Electrical signals in the brain travel through nerves to muscles

input question: What is the missing first step of the following process: - Nephrons in the kidney filter the blood - The waste that is filtered out mixes with water - Become urine - Ureters carry urine out of the kidneys.???
output answer: Blood carried into kidney by the renal artery

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