Final answer:
The "Age of an American penny" is classified as quantitative data, with the observational unit being the American penny itself, since age is a measurable characteristic of the penny. Option d. is correct.
Step-by-step explanation:
The variable "Age of an American penny" would be classified as quantitative, because it represents a measurement that can vary numerically. The observational unit in this context is the American penny itself, as the age is a characteristic that describes the penny. Hence, the correct classification of the variable and observational unit would be: Quantitative, Observational unit: American penny.
To further elaborate, quantitative data is information that can be measured and written down with numbers. For example, the "number of cars in a parking lot" is quantitative discrete data, whereas the "distance from your home to the nearest grocery store" is quantitative continuous data. Conversely, categorical or qualitative data puts things into categories without expressing them in numbers, such as the "colors of houses" or a person's existing "political party affiliation". Therefore, the age of an American penny is a numerical value representing how many years old the penny is, which is a characteristic that can be precisely measured and is indeed quantitative.