Betelgeuse is one of the brightest stars in the night sky even though it is 640 LY from Earth. Barnard's Star, on the other hand, is relatively close but is not visible to the unaided eye.
Which of the following is a correct explanation for this?

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.