Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the oxidation state changes from

The set of correct statements is:

(i) Manganese exhibits $+7$ oxidation state in its oxide.

(ii) Ruthenium and Osmium exhibit $+8$ oxidation in their oxides.

(iii) $\mathrm{Sc}$ shows $+4$ oxidation state which is oxidizing in nature.

(iv) $\mathrm{Cr}$ shows oxidising nature in $+6$ oxidation state.

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): The first ionization enthalpy of $3\mathrm{d}$ series elements is more than that of group $2$ metals

Reason (R): In $3\mathrm{d}$ series of elements successive filling of $\mathrm{d}$-orbitals takes place.

In the light of the above statements, choose the correct answer from the options given below:

Which of the following elements have half-filled f-orbitals in their ground state ?
(Given : atomic number $\mathrm{Sm}-62;\mathrm{Eu}=63;\mathrm{Tb}=65;\mathrm{Gd}=64,\mathrm{Pm}=61$)

Choose the correct answer from the options given below :