Answer:
<em>The correct option is theories. </em>
Explanation:
A scientific theory is a detailed explanation of natural researches which are supported through evidence. Scientific theories can be changed if other evidence are made which support another theory. Hence, scientific theories can change. The concepts of plate tectonics and evolution change overtime whenever new pieces of evidence are discovered. Hence, they are scientific theories.
Other options such as hypotheses are not correct because a hypothesis is just a tentative statement which can either be proved to be correct or wrong. Observations are not made on evidences hence the option observations is also not correct.
A lake community with four trophic levels suddenly suffers from algal blooms. Using the strategy of biomanipulation, an ecologist may propose removing zoonplankton.
Hope I helped.
It’s thin compared to the other layers (core, mantle etc) and is comprised of rocks so it is hard.
