The material used in the nuclear industry as protective shields and control rods is

The correct statement$(s)$ for orthoboric acid $(H_3BO_3)$ is/are:
$(A)$ It behaves as a weak acid in water due to self-ionization.
$(B)$ Acidity of its aqueous solution increases upon addition of ethylene glycol.
$(C)$ It has a three-dimensional structure due to hydrogen bonding.
$(D)$ It is a weak electrolyte in water.

Aluminum dissolves in mineral acids and aqueous alkalis and thus shows amphoteric character. $A$ piece of aluminum foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning match stick near the mouth of the test tube,a pop sound indicates the evolution of hydrogen gas. The same activity when performed with concentrated nitric acid,the reaction does not proceed. Explain the reason.

The stability of $+1$ oxidation state among $Al$,$Ga$,$In$ and $Tl$ increases in the sequence:

Given below are two statements:
Statement $I$: Aluminium is more electropositive than thallium as the standard electrode potential value of $E^\circ_{Al^{3+}/Al}$ is negative and $E^\circ_{Tl^{3+}/Tl}$ is positive.
Statement $II$: The sum of first three ionization enthalpies of boron is very high when compared to that of aluminium. Due to this reason, boron forms covalent compounds only and aluminium forms $Al^{3+}$ ion.

The correct order of atomic radii of group $13$ elements is