Cigarette or gas lighter is made up of

Which oxide of manganese is amphoteric in nature?

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:

The false statement about iron $(III)$ hydroxide is that

Which of the following statements is true for $Fe_3O_4$?

What is the use of potassium dichromate $(K_2Cr_2O_7)$?