Which of the following elements forms a molecule consisting of eight of its own atoms?

Identify the incorrect statement about $SiO_2$ (silica) from the following.

Which of the following pairs of elements form amphoteric oxides?

In the laboratory,silicon can be prepared by the reaction:

Give a brief account of the production of cement and write its properties and uses.

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: