Which of the statements about glass are correct? 1. Glass is a super-cooled liquid having infinite viscosity 2. Violet coloured glass is obtained by adding MnO2 3. Glass is a man-made silicate 4. Glass is a crystalline substance Select the correct answer using the code given below:

• A. 1, 2 and 3
• B. 1, 2 and 4
• C. 2, 3 and 4
• D. 1 and 3 only