The correct answer is transmission<<<<<<
Lead-207 can change into Lead-208.
When Lead-207 is bombarded with neutrons, the atom acquires the neutron. Adding a neutron only changes the mass number of the atom. This does not involve change in the identity of the atom. So, Lead-207 can change into Lead-208 without change in its chemical properties.
It is formed from mantle material
Ground water keept the ground at a stable level when it is gone the cavern it was in has no support and is at risk of callaps