Which hydrated elements of group $13$ are found as polymers in nature?

Which one of the following elements does not form triiodide on reacting with iodine?

What is the formula for meta-boric acid?

Borazine,also known as inorganic benzene,can be prepared by the reaction of $3$ equivalents of "$X$" with $6$ equivalents of "$Y$". "$X$" and "$Y$",respectively,are:

Which of the following hydroxides is acidic?

For a $p$-block element,its $3d, 3s, 3p$ and $4s$ orbitals are completely filled and the differentiating electron goes to the $4p$ orbital. The element should have its atomic number in the range: