Concept:
In library classification systems, notation refers to the symbols used to represent subjects. Different schemes use different types of notation such as pure numeric, pure alphabetic, or mixed notation.
Step 1:Understanding mixed notation.
Mixed notation uses a combination of letters and numbers to represent subjects in a classification system.
Step 2:Identifying the scheme using mixed notation.
The Library of Congress Classification (LCC) system uses a combination of alphabetic and numeric symbols, which makes it a mixed notation system.
For example: QA76.73 represents a subject within computer science.
Step 3:Conclusion.
Since the Library of Congress Classification uses both letters and numbers, the correct answer is Option (D).