The actinoids exhibit, more member of oxidation states in general than the lanthanoids. This is because
A. the actinides are more reactive than the lanthanides
B. the `5f`-orbits are more buried than the `4f`-orbits
C. there is a similarity between `4f`and `5f`-orbits in their angular part of the wave function.
D. the `5f`-orbits extend farther from the nucleus than the `4f`-orbitals.