The decreasing order of basic character of $K_2O$, $BaO$, $CaO$ and $MgO$ is

Which block elements in the modern periodic table are the most electropositive?

The set of amphoteric oxides among $ZnO$,$Tl_2O_3$,$In_2O_3$,$B_2O_3$,$PbO$,$SnO_2$ is

Match List-$I$ with List-$II$.

List-$I$ (Oxide)	List-$II$ (Nature)
$A. Cl_2O_7$	$I. Amphoteric$
$B. Na_2O$	$II. Basic$
$C. Al_2O_3$	$III. Neutral$
$D. N_2O$	$IV. Acidic$

Choose the correct answer from the options given below:

The first $\left( \Delta_{i}H_{1} \right)$ and the second $\left( \Delta_{i}H_{2} \right)$ ionization enthalpies (in $kJ \ mol^{-1}$) and the $\left( \Delta_{eg}H \right)$ electron gain enthalpy (in $kJ \ mol^{-1}$) of a few elements are given below:

Elements	$\left( \Delta_{i}H_{1} \right)$	$\left( \Delta_{i}H_{2} \right)$	$\left( \Delta_{eg}H \right)$
$I$	$520$	$7300$	$-60$
$II$	$419$	$3051$	$-48$
$III$	$1681$	$3374$	$-328$
$IV$	$1008$	$1846$	$-295$
$V$	$2372$	$8581$	$+48$
$VI$	$738$	$1451$	$-40$

Which of the above elements is likely to be:
$(a)$ the least reactive element.
$(b)$ the most reactive metal.
$(c)$ the most reactive non-metal.
$(d)$ the least reactive non-metal.
$(e)$ the metal which can form a stable binary halide of the formula $MX_{2}$ ($X =$ halogen).
$(f)$ the metal which can form a predominantly stable covalent halide of the formula $MX$ ($X =$ halogen)?

In which of the following are the oxides of three elements $X, Y$ and $Z$ correctly arranged in the increasing order of acidic nature? The electronic configurations of $X, Y$ and $Z$ are $[Ne] 3s^2 3p^1$,$[Ne] 3s^2 3p^5$,and $[Ne] 3s^2$ respectively.