Which of the following has the lowest melting point?

In $P_4O_{10}$,the number of oxygen atoms attached to each phosphorus atom is

Which of the following does not exist?

The $(Si_2O_5)_n^{2n-}$ anion is obtained when:

Mention the catenation order for group $14$ elements.

Identify the correct statements from the following:
$(a)$ $CO_{2(s)}$ (dry ice) is used as a refrigerant for ice-cream and frozen food.
$(b)$ The structure of $C_{60}$ contains $20$ six-membered rings and $12$ five-membered rings.
$(c)$ $ZSM-5$,a type of zeolite,is used to convert alcohols into gasoline.
$(d)$ $CO$ is a colorless and odorless gas.