The answer is Pennsylvanian. I worked on this before. The Pennsylvanian era is a subperiod of the Carboniferous Period. i really hope this helps :)
I think your answer is b based off the information I inquired
second I believe is A lemme know if I helped
Explanation:
waterfalls are temporary features of rivers because stream erosion is greatest at waterfalls and rapids. The water that falls at the base of the waterfall erodes rock there, leaving the rock at the tops of the waterfalls to overhang. Overall, undermining causes waterfalls to recede farther upstream.
Crust:outer silicate solid crust
mantle:highly viscous
core:solid inner core
"<span>What contributed to the formation of the majority of Iceland?"
Lava is the answer, I believe.</span>