1. A gas at 20 degrees C may be considered rarefied, deviating from the continuum concept, when it contains less than1012molecules per cubic millimeter. If Avogadro’s number is 6.0231023molecules per mole, what absolute pressure(in Pa) for air does this represent?

bcde is the incorrect answer it is a

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.