The plasma membrane is the cell structure you are looking for.
The controlis the plant with just water. The independent variable is the plants. The dependaent is the amout of salt in the water.
The indepedent is the trees. The dependent is the greenhouse or no greenhouse.
Concrete is a composite, since it is composed of various elements like, sand, gravel & water. When mixed together with the proper measurements, it produce cement which is used for building construction, road concreting, etc.
Answer:
<h3>the right answer is option B</h3>