Part A: Identifying Variables
Read the following hypotheses and identify the variables.

If the number of cigarettes smoked increases, then the risk for lung cancer increases.
Independent variable:
Dependent variable:
If the number of sharks swimming in a coastal region increases, then the number of shark attacks on humans will also increase.
Independent variable:
Dependent variable:
If the amount of milk a person drinks increases, the strength of his or her bones will stay the same.
Independent variable:
Dependent variable:

Answer/Explanation:

There are usually two types of variables in a an hypothesis in a typical research study. These are independent variable, and dependent variable.

The independent variable is the variable that is usually manipulated, which causes a change on the dependent variable. On the other hand, the dependent variable is the variable that changes as a result of the change that occurs on the independent. A change on the independent variable, causes a change on the dependent variable. In other words, the dependent variable is dependent on the independent variable that is being changed or manipulated. The dependent variable is what is being measured or tested in a research study.

In the hypotheses stated in the question above, the independent variable and dependent variable for each are listed as below:

First hypothesis:

Independent variable:  number of cigarettes smoked

Dependent variable: risk for lung cancer

Second Hypothesis:

Independent variable: number of sharks swimming

Dependent variable: number of shark attacks on humans

Third Hypothesis:

Independent variable: amount of milk

Dependent variable: strength of a person's bones

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.