The answer is D but I gotta make this answer 20 characters real quick so ignore what I'm saying ja ja ja the cat go wow the I guess on this and I answer it a but the dog go wolf wolf moo
Answer: Lanthanide and actinide series
Explanation: The elements with partially or fully filled f orbitals belong to f block elements.
f block elements include lanthanides and actinides. They are called so the lanthanides contain the first element named as lanthanum and actinides contain first element named as actinium. They are also called as inner transition elements.
All of them have general electronic configuration:
, where n = 6-7
<span>Heavy metals like mercury enter waterways by industrial dumping and poor regulatioin of effluent, and they also enter soil through a similar manner, in which waste is disposed of imporperly. Another source of heavy metals are the gases leaving industry carrying these metals. The metals fall as a solid on to soil and water ways. Therefore, the answer is D.</span>