What does a in the type of examination question measure?

The "a" in the type of examination question doesn't inherently measure anything on its own. It's not a standard notation within educational assessment. To understand what a specific "a" might measure, you need to provide the full context of the question type.

For example, if you're referring to a multiple-choice question with options a, b, c, and d, the "a" simply labels one of the answer choices. It doesn't measure anything directly; the question itself measures a student's knowledge or understanding of a specific concept.

If you can provide more information about the question type (e.g., "Type A essay question," or the specific wording of the question including any "a" notation), I can give you a more accurate answer.