B. Crystalline structure
C. Types of chemical elements
And
D. Amounts of chemical elements
Astronomy can best be described as a "<span>a. study of objects beyond earths atmosphere", although the subject of astronomy can be much more complicated. </span>
Because tropical levels used to be broken because temperatures hasn't varied in the years and history of global temperatures and history.
Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or changed, by the body into moving mechanical energy and heat energy. People have invented ways to use the chemical energy of substances to power machines.
