Amphibole silicate structure has '$x$' number of corners shared per tetrahedron. The value of '$x$' is

Which of the following species does not exist?

Carbon on reaction with hot conc. $H_2SO_4$ gives two oxides along with $H_2O$. What is the nature of these two oxides?

Which of the following oxides is amphoteric in nature?

The name of the structure of silicates in which three oxygen atoms of $[SiO_4]^{4-}$ are shared is :-

$(a)$ Classify the following oxides as neutral,acidic,basic,or amphoteric:
$CO, B_2O_3, SiO_2, CO_2, Al_2O_3, PbO_2, Tl_2O_3$
$(b)$ Write suitable chemical equations to show their nature.