Aqueous solution of which of the following boron compounds will be strongly basic in nature?

Identify the correct statement for $B_2H_6$ from those given below.
$(A)$ In $B_2H_6$,all $B-H$ bonds are equivalent.
$(B)$ In $B_2H_6$ there are four $3$-centre-$2$-electron bonds.
$(C)$ $B_2H_6$ is a Lewis acid.
$(D)$ $B_2H_6$ can be synthesized from both $BF_3$ and $NaBH_4$.
$(E)$ $B_2H_6$ is a planar molecule.
Choose the most appropriate answer from the options given below.

The Lewis acid character of boron trihalides follows the order:

Two gases when mixed give white dense fumes,the gases are

Which pair of oxides is acidic in nature?

Common alum is