Final answer:
The valid library name (libref) from the options provided is 'car2010' as it adheres to the naming conventions by starting with a letter and being followed by letters and numbers. c. car2010
Step-by-step explanation:
The question is about the rules for naming a library reference, known as a libref, in programming contexts, such as in SAS (Statistical Analysis System). A valid libref must start with a letter (A-Z, a-z) and can be followed by up to seven more characters that can be letters, numbers, or underscores.
Based on these rules, the valid libref from the options provided is c. car2010. It starts with a letter and contains only letters and numbers, adhering to the libref naming conventions. Conversely, 'a. 2010Car' starts with a number, 'b. car/2010' contains an illegal character (slash), and 'd. cars_2010' exceeds the maximum length limit for a libref.