Which statement is true about this reaction? Superscript 14 subscript 7 upper N plus superscript 1 subscript 1 upper H right arrow superscript 15 subscript 8 upper O.

a
Its product is heavier than each of its reactants.
b
It is a practical source of energy on Earth.
c
It occurs only outside the solar system.
d
It shows the critical mass of an element.