Which transition element of the $3d$ series is used in a dry battery cell?

On heating $Mn(OH)_2$ with $PbO_2$ and conc. $HNO_3$,a pink colour is obtained due to the formation of:

Give the preparation of potassium dichromate and state its uses.
Give the structures of chromate and dichromate ions. How can chromates and dichromates be interconverted?
Give the chemical reactions showing the oxidizing nature of potassium dichromate.

In the reaction $4K_2Cr_2O_7 \xrightarrow{\text{heat}} 4K_2CrO_4 + 3O_2 + X$,identify $X$.

Which of the following statements are $INCORRECT$?
$A$. All the transition metals except scandium form $MO$ oxides which are ionic.
$B$. The highest oxidation number corresponding to the group number in transition metal oxides is attained in $Sc_2O_3$ to $Mn_2O_7$.
$C$. Basic character increases from $V_2O_3$ to $V_2O_4$ to $V_2O_5$.
$D$. $V_2O_4$ dissolves in acids to give $VO_4^{3-}$ salts.
$E$. $CrO$ is basic but $Cr_2O_3$ is amphoteric.
Choose the correct answer from the options given below:

Choose the correct statements from the following:
$A$. $Mn_2O_7$ is an oil at room temperature.
$B$. $V_2O_4$ reacts with acid to give $VO^{2+}$ ions.
$C$. $CrO$ is a basic oxide.
$D$. $V_2O_5$ does not react with acid.
Choose the correct answer from the options given below: