Which of the following statements regarding the magnetic properties and electronic configurations of lanthanoid ions is correct?

1. A.The magnetic moment of ${\text{Sm}}^{3+}$ is calculated using the spin-only formula.
2. B.${\text{Eu}}^{3+}$ has a $4f^6$ configuration and exhibits temperature-independent paramagnetism.
3. C.${\text{Gd}}^{3+}$ has a magnetic moment of $7.9\text{ BM}$ due to its $4f^7$ configuration.
4. D.The magnetic moment of ${\text{Ce}}^{3+}$ is significantly lower than the spin-only value.