To determine which of the statements are random variables, let's recall that a random variable is a numerical outcome of a random process. This means the variable must be capable of taking on different numerical values depending on the outcome of a random event.

1. The amount of rain, in inches, that will fall next Friday in Dallas, TX: This is a numerical value (in inches), and it depends on random weather conditions. So, this is a random variable.

2. The major of a randomly drawn student from Arizona State University: This is a categorical variable (major is a category, not a number). Since a random variable must be numerical, this is not a random variable.

3. The number of books purchased next year by your local library: This is a numerical value, and it depends on various random factors (like budget, demand, etc.). So, this is a random variable.

Based on the analysis:

• i and iii are random variables, but ii is not.

Thus, the correct answer is