Boron cannot form which one of the following anions?

$Al_2O_3$ reacts with

Given below are two statements:
Statement $I$: Boron is extremely hard,indicating its high lattice energy.
Statement $II$: Boron has the highest melting and boiling point compared to its other group members.
In the light of the above statements,choose the most appropriate answer from the options given below:

An element $X$ which occurs in the first short period has an outer electronic structure $s^2p^1$. What are the formula and acid-base character of its oxides?

Which of the following structures is similar to graphite?

The most acidic of the following compounds is