Why was narcissus turned into a flower?
a.
because it was the reward for completing all of the 12 labors
b.
because the 10-year journey home proved to be too strenuous
c.
because he gave the gift of fire to the mortals
d.
because he fell in love with his own reflection

because he fell in love with his own reflection--he was turned into a flower after pining away over his reflection. 

Narcissus was punished for his behavior of being in love with or obsessed with his own beauty. He could not appreciate any beauty in anything or anyone else. He then killed himself and the flower appeared where he died as he quested after his reflection in the water. 

D. Because he fell in love with his own reflection.
Hope this helps :)