Identify the factor responsible for the greater range of oxidation states in actinoids.

Which of the following factors may be regarded as the main cause of lanthanide contraction?

What is the value of spin only magnetic moment for $\text{Cu}^{2+}$ in BM?

Which of the following ions exhibit same value of spin only magnetic moment?
(A). $\text{Ti}^{3+}$
(B). $\text{Cr}^{3+}$
(C). $\text{Mn}^{2+}$
(D). $\text{Fe}^{3+}$
(E). $\text{Sc}^{3+}$
Choose the most appropriate answer from the options given below.