Which pair of elements has the same number of electrons in their valence shell$:-$

What is the correct order comparing the acid strengths of $HF$,$HCl$,$HBr$,and $HI$?

Arrange the following oxides in the increasing order of their basic nature: $(a) Al_2O_3, (b) K_2O, (c) P_2O_5, (d) MgO$.

Given below are two statements :
Statement $I$ : An element in the extreme left of the periodic table forms acidic oxides.
Statement $II$ : Acid is formed during the reaction between water and oxide of a reactive element present in the extreme right of the periodic table.
In the light of the above statements,choose the correct answer from the options given below :

The elements with the following atomic numbers belong to the same group:

In which of the following,the elements $Al, B, Mg$ and $K$ are correctly arranged in the increasing order of their metallic character?