How is stained glass made?
a.
adding metallic oxides to sand and ash or lime, then infusing at high temperatures
b.
adding metallic oxides to salt, then infusing over time at low temperatures
c.
adding metallic oxides to sulfur, then infusing at high temperatures
d.
adding metallic oxides to sulfur, then infusing at low temperatures

select the best answer from the choices provided

a
b
c
d