Final answer:
The correct formula for making stained glass is sand, cobalt oxide, lime, and heat; wherein sand provides silica, lime adds durability, cobalt oxide gives the blue color, and heat melts the ingredients together.
Step-by-step explanation:
The correct formula for making stained glass involves several key ingredients including sand (silica, SiO₂), lime (CaO), and various metal oxides for coloring. Among the options provided, the one that includes the essential components needed to form the glass matrix and the cobalt oxide for blue coloring is option 'c' which is sand, cobalt oxide, lime, and heat. Sand acts as the foundational silica source, lime (calcium oxide) adds durability, cobalt oxide provides the blue pigment, and heat is applied to melt and mix these materials together, allowing for the creation of stained glass.