When you expect something, but get something else, you have a reason big enough to ask new questions and start a new investigation.
Example:
If you create a tree by artificially breeding different species, and then plant it with certain expectations in width, size, bark width, leaf shape, etc. and things go differently, a new investigation might begin with a whole new load of questions.
Answer:

Hope it helped,
Happy homewok/ study/ exam!
The correct answer is "reefs".
Shallow-marine environments are considered to be an area among the shore and deeper water, along with a reef wall or a shelf break. This surroundings is characterized by means of oceanic, geological and organic conditions, as described underneath.
So, if the birthrate and the death rate are the same, that means that for every person that gets born, one person dies: so the number of people would stay constant. This means that the growth rate is actually 0%.