This term refers specifically to chain or series of large metropolitan areas.
a) megalopolis
b) sprawl
c) suburban
d) urban

When a lake, river or other aquatic  system  becomes  eutrophic, it can have serious negative effects on other organisms like fish, birds and even people.if an algal bloom is so bad that it causes wide-spread death  in  the  water, the organisms that die will all sink to the bottom and start to decompose.

2pi more meters because you find the circumference which is 6pi and 4pi and subtract it and you get 2pi