Which one of the following elemental forms is not present in the enamel of the teeth?

In $C_{60}$,all carbon atoms are .......

Which metal is used in radiation shields?

Given below are two statements:
Statement $I$ : $SiO_2$ and $GeO_2$ are acidic while $SnO$ and $PbO$ are amphoteric in nature.
Statement $II$ : Allotropic forms of carbon are due to property of catenation and $p \pi-d \pi$ bond formation.
In the light of the above statements,choose the most appropriate answer from the options given below:

The hybridisation of elements present in fullerene and graphite are respectively.

Which one of the following is a correct set?