input question: What is the missing first step of the following process:  -  Over long periods of time rain can hit the limestone - And cause a acidic reaction - The limestone will slowly disintegrate - A large gap with be where the limestone was - Result in the cave.???
output answer: Some of the rock in the ground is made of limestone

input question: What is the missing first step of the following process:  -  The parent(s) incubate the eggs - The eggs hatch - The mother (and sometimes the father) bird take care of the baby birds - The baby birds grow up and get their flight feathers - The young birds learn to fly and leave the nest - The adult birds find mates and mate.???
output answer: A bird lays eggs in a nest

input question: What is the missing first step of the following process:  -  Oxygen moves from the lungs into the bloodstream - Air is pushed through the vocal chords - A person talks - Other air is pushed out of the lungs into the environment.???
output answer: Air is pulled into the lungs

input question: What is the missing first step of the following process:  -  The oxygen travels into the lungs - The oxygen binds to hemoglobin proteins within erythrocytes (red blood cells) - The erythrocytes are pumped through the body by the heart - All cells receive the oxygen.???
output answer: