<span>Refraction is where the direction of travel of sound waves is altered by passing through a material of much higher or lower density. Walls that allow sound through are one example, but answer B is more about walls bouncing sound back - that's an example of reflection. The most likely change of density is answer A, air with big temperature differences.</span>
The combination of symbols that shows the ratio of elements
in a compound is called chemical formula. A chemical formula is one of the ways
in expressing information about the ratio and proportion of atoms that consists
a particular chemical compound. This is done by using a single line pf chemical
symbols of elements, numbers, and sometimes parentheses, comma, dashes,
brackets and sometimes the positive and negative sign. Chemical formula can
completely specify the simplest structure of molecules and chemical substances.
The answer to this question is B....hope this helps.
