Which of the following oxides is amphoteric?

Graphite is used as a dry lubricant because of its

The correct order of catenation is

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

State True or False for the following statements:
$(1)$ Oxides of indium and thallium are basic in their properties.
$(2)$ $C$,$Si$ are non-metals,while germanium,tin,and lead are high melting metals.

Rationalise the given statements and give chemical reactions:
$1$. Lead $(II)$ chloride reacts with $Cl_2$ to give $PbCl_4$.
$2$. Lead $(IV)$ chloride is highly unstable towards heat.
$3$. Lead is known not to form an iodide,$PbI_4$.