Which of the following is a correctly worded performance component of an instructional objective?

A well-constructed performance component of an instructional objective is clear, measurable, and indicates a specific behavior that can be observed and assessed. In this context, the first choice states that "the student will be able to attach a regulator to the valve." This statement is specific and outlines a direct action that the student is expected to perform, making it easy to evaluate their ability through assessment in a practical setting.

In contrast, the other options contain elements that are less concrete. For instance, the second choice revolves around understanding the importance of safety equipment, which is subjective and not directly observable. The third choice mentions knowing how to operate a dive computer, which again lacks the clarity of a specific, measurable action, as "knowing" cannot be directly assessed without observing the student in action. Finally, the fourth choice focuses on having an appreciation for underwater environments, a sentiment that is inherently abstract and difficult to measure through performance criteria.

Thus, choice A stands out as it fulfills the criteria for an effective instructional objective—being both specific and directly measurable.