Final answer:
The statement in question refers to the use of fractions to write ratios and rates, which compare two quantities and can involve different units of measure. The correct answer is 'fractions'.
Step-by-step explanation:
Ratios and rates each compare two numbers by using fractions. However, they compare two measurements that involve different units of measure. Therefore, the correct answer to the statement is that ratios and rates are written using fractions. Ratios can be expressed in various forms such as 2/3, 2:3, or "2 to 3". A proportion is a statement that two ratios are equivalent, like 1/2 = 3/6. Meanwhile, a unit rate is a ratio in which one of the quantities compared has a value of 1, such as 55 miles per 1 hour. Lastly, a unit scale is a special type of ratio that compares real-life measurements to those in a scale drawing or model, like 1 inch on a map representing 100 feet in reality.