In general,the properties that decrease and increase down a group in the periodic table respectively are

Which one among the following statements is/are not correct?
$I$. $Ba$ compounds,generally are more covalent than $Be$ compounds.
$II$. The electron gain enthalpy of $He$ is positive.
$III$. The oxidation state of $O$ in $OF_2$ and $Na_2O$ are same.
$IV$. The radius of $Na^{+}$ ion is smaller than that of $F^{-}$ ion.

Which of the following set of properties generally decreases along a period?

Point out the wrong statement: On moving horizontally from left to right across a period in the periodic table

Match List-$I$ with List-$II$:

List-$I$ (Atomic Number)	List-$II$ (Block of periodic table)
$A$. $37$	$I$. $p$-block
$B$. $78$	$II$. $d$-block
$C$. $52$	$III$. $f$-block
$D$. $65$	$IV$. $s$-block

Choose the correct answer from the options given below:

Which one of the following sets of ions represents the collection of isoelectronic species?