input question: What is the missing first step of the following process:  -  The virus has receptors that lock onto a target cell - The virus enters the cell - The virus uses the cell like a factory to make new copies of the virus - The new copies of the virus leave the cell - Infect other cells - The host gets sick as its cells are damaged.???
output answer: A virus enters a host body

input question: What is the missing first step of the following process:  -  Blood is carried to the kidneys through the renal arteries - The kidneys contain filters inside - The filters capture the waste products - The waste is combined with water to make urine - The urine leaves the kidney and is collected in the bladder - The cleaned blood is returned to the body.???
output answer: Waste products are deposited in the blood

input question: What is the missing first step of the following process:  -  Your thermostat sends a signal to your heating system to provide heat for your home - When your oil burner is engaged, heating oil travels from the tank to the burner by way of a pump - Here the oil becomes a fine mist mixed with air - The fuel/air mixture is then injected into the burner where it is ignited in the combustion chamber - The warm air is disbursed through vents, hot water through baseboards, or by steam radiators -???
output answer: Your thermostat senses that the room temperature has fallen below your thermostat setting

input question: What is the missing first step of the following process:  -  Ice inside the cloud bumps around and causes electrostatic charges - The cloud becomes a thundercloud - Electrostatic energy builds and forms a strong negative charge - Positive energy is attracted to the negative energy in the cloud - This positive energy gathers on the ground - The positive energy connects with the negative energy and forms lightning.???
output answer:
Ice forms inside a cloud