Discuss how can the effects of fabrication errors and different temperatures be handled?

I have most of the problem done but I need help with parts 9 10 and 11. Thank you!

Why does quartz have many different shades and color?

Which of the glass do you select from the table below to join silicon carbide (SiC) rods. Justify your answer and show complete work. Elastic modulus Thermal expansion (GPa) Material/properties Thermal coefficient (x10/°C (MPa.m2) | conductivity (W/m.K) 120 at 25-1000°C) SiC 410 4.0 4.6 Glass I 70 0.5 0.6 1.38 Glass II 75 4.5 1.0 2.00 Glass III 72 8.0 1.0 2.00