To support life, why must a planet have a roughly circular orbit around a star? a. so freshwater is available b. to keep the proper air molecules in the atmosphere c. to support chemical reactions d. for temperature regulations

The phlogiston theory in the 17th century attempted to explain burning. the theory stated that combustable objects contained a material called phlogiston, a substance without mass, color, odor, etc. after objects burned, the objects were dephlogistonated and were then in their true form. the phlogiston theory was accepted until the 18th century, when lavoisier proved that combustion requires a gas that has mass. phlogiston is considered a) to be scientific knowledge b) not to be scientific knowledge c) to be proven by scientific method d) to be accepted in the modern scientific community

The oxidizing agent our bodies use to obtain energy from food is oxygen (from the air). if you breathe 15 times a minute (at rest), taking in and exhaling 0.5 l of air with each breath, what volume of air do you breathe each day? air is 21% oxygen by volume. what volume of oxygen do you breathe each day?

Time ! for a smell to begin the process of registering in your brain, first you must a) inhale odor molecules into the nasal cavity b)transduce scent chemicals c)have a scent to inhale d)all answers can work