The transition metal used as a catalyst is

Given below are two statements:
Statement $I$: The number of pairs, from the following, in which both the ions are coloured in aqueous solution is $3$: $[Sc^{3+}, Ti^{3+}], [Mn^{2+}, Cr^{2+}], [Cu^{2+}, Zn^{2+}]$ and $[Ni^{2+}, Ti^{4+}]$.
Statement $II$: $Th^{4+}$ is the strongest reducing agent among $Th^{4+}, Ce^{4+}, Gd^{3+}$ and $Eu^{2+}$.
In the light of the above statements, choose the correct answer from the options given below:

The number of statement$(s)$ correct from the following for copper (atomic number $29$) is/are $...$
$(A) \ Cu(II)$ complexes are always paramagnetic
$(B) \ Cu(I)$ complexes are generally colourless
$(C) \ Cu(I)$ is easily oxidized
$(D)$ In Fehling solution,the active reagent has $Cu(II)$

The transition metals have a less tendency to form ions due to

Which of the following orders is correct?

Which of the following is not arranged in the correct sequence?