Environment in which coal can form

hi there the answer is

from google:

"coal formed millions of years ago when the earth was covered with huge swampy forests where plants - giant ferns, reeds and mosses - grew. as the plants grew, some died and fell into the swamp waters."

- decrease the number of plants and animals living in the water.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.