Answer:
I believe the answer is B
Explanation:
Don't quote me
Controlled population growth.
Explanation:
US is a highly developed country and it has expansive infrastructure and highly mechanized agricultural equipments. So first option is not a choice. Second, access to chemical fertilizers and pesticides in a country with such advanced agriculture infrastructure is very easy. Third US is well known for using GM crops.
US does not have a controlled population growth because if not the birth rate then migration of people to US is a major concern for that country. Thus, this will be a correct choice for the given question.
Answer:
As the variables are not given, let us help with general explanation on manipulated variable.
Explanation:
A manipulated variable is an independent variable. In a scientific experiment, an independent variable can be described as a variable which can change naturally or which is changed by the researcher to check its effect on the dependent variable. The dependent variable is the variable which is under study and being tested.
For example, to check the difference in photosynthesis rate by light, the amount of light will be the independent variable and the rate of photosynthesis will be the dependent variable.
Niches, trophic levels, and ecological processes of a biological community.
Yes,oxygen-rich blood is carried through pulmonary arteries from the lungs to the heart.