(i) This is a crystalline solid.

(ii) Refractive index is the same in all the directions.

(iii) This has a definite heat of fusion.

(iv) This is also called supercooled liquid.

Correct Answers:

(i) This is a crystalline solid.

(iii) This has a definite heat of fusion.

Explanation:  Quartz glass is an amorphous solid and they do not have a definite heat of fusion.