Which of the following compounds is used in cosmetic surgery?

Identify the correct statements from the following.
$i$. Melting points and boiling points of group $13$ elements are much higher than those of corresponding group $14$ elements.
$ii$. $SiO$ only exists at high temperatures.
$iii$. $PbI_4$ does not exist.
$iv$. Buckminster fullerene contains twelve $6$-membered carbon rings and twenty $5$-membered carbon rings.

Mention the uses of pure forms of germanium and silicon.

For a good quality cement,the ratio of silica to alumina is found to be

The plague of tin is the:

Silicon is an important constituent of which of the following?