Which is characteristic of soil horizons?

A. Boundaries between soil horizons are usually transitional rather than sharp.
B. All of these
C. They are classified by letters.
D. They can be distinguished from one another by appearance and chemical composition.

Answermongolia;

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.