The element which shows only one oxidation state other than its elemental form is :

Choose the correct statements from the following

A. $$\mathrm{Mn}_2 \mathrm{O}_7$$ is an oil at room temperature

B. $$\mathrm{V}_2 \mathrm{O}_4$$ reacts with acid to give $$\mathrm{VO}_2{ }^{2+}$$

C. $$\mathrm{CrO}$$ is a basic oxide

D. $$\mathrm{V}_2 \mathrm{O}_5$$ does not react with acid

Choose the correct answer from the options given below :

Identify correct statements from below:

A. The chromate ion is square planar.

B. Dichromates are generally prepared from chromates.

C. The green manganate ion is diamagnetic.

D. Dark green coloured $$\mathrm{K}_2 \mathrm{MnO}_4$$ disproportionates in a neutral or acidic medium to give permanganate.

E. With increasing oxidation number of transition metal, ionic character of the oxides decreases.

Choose the correct answer from the options given below: