The answer is B. In order to test something out you need to be able to solve it.
Answer:
4th line
Explanation:
-water cycle helps regulate the temperature on the Earth.
Answer:
The two main variables in an experiment are the independent and dependent variable. An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable. A dependent variable is the variable being tested and measured in a scientific experiment.
To supply oxygen to the body, the respiratory system works closely with the circulatory system. As oxygen is taken in into the lungs, it travels through blood vessels, which then circulate oxygen-rich blood to cells and tissues.
