Answer:
The correct answer is - А. experiment.
Explanation:
An experiment is a type of research method used for scientific investigation to check how a natural phenomenon works and how a particular variable affected by causing or manipulating one variable.
The affected variable called the dependent variable and the variable that is changed is called the independent variable. Other than independent variables other variables should be controlled so there would be no influence on the result other than independent varibles.
D) The basic unit of structure and function in all living things
Organic molecules, which are found mostly in food. These molecules have C-C or C-H bonds, which are high energy bonds.
-~90% of atmospheric oxygen is produced in
the photic zone
-Seasonal turnover leads to consistent oxygen
levels
--Phytoplankton, algae, photosynthetic
organisms produce oxygen
--Highly oxygen-rich, but
nutrient-poor water.....:)
