Answer:
C. naturally uncombined with other elements.
Explanation: Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air.
Answer:
Density of a quantity of matter is its mass divided by its volume. The mass of an object depends on the atomic mass of the individual atoms or molecules and the how close the they are compressed together.
Explanation:
I think Magnesium not sure because the relative atomic mass of magnesium is 24,31.
100 mm = 100/1000= .1 meters
1cm = 1/100 = .01m
10 decimeters = 10/10 = 1 meter
.0001 km = .0001*1000 = .1 meter
