harmless, a sheet of paper
Alpha particles do not possess a high amount of energy and are not very ionizing, since they have a high mass. This makes them relatively safer to work with.
The answer is D. They already knew about animals, plants and skin.
<u>Answer </u>
kinetic
<u>Explanation</u>
Matter is anything that occupies space and has mass. There are four states of matter, solids, liquids, gases and plasma. All this consist of small molecules that are in constant random motion. This is called kinetic theory of matter.
When these molecules are in motion they may collide. No energy is gained or lost during collision. The particle/molecules move in a constant linear motion.
the answer to this question is B