Question

Ceramics make excellent refractory materials. A material is said to be refractory if it:

1 has high refractive index
2 retains its strength at high temperatures
3 resists the flow of electric current 4 all of the mentioned

Answer 1

Option 2 is the correct answer

Step-by-step explanation:

Ceramics, which mainly consist of oxides, carbides and nitrides, can withstand very high temperatures; furnaces are generally lined with such ceramics.