Which of the following is an instructional objective?

The selection of "Students will use fractions in an experiment" as the instructional objective highlights its focus on a specific outcome that can be measured and assessed. Instructional objectives are designed to outline clear expectations for what students should be able to do after a lesson, emphasizing measurable skills or knowledge.

In this case, using fractions in an experiment indicates that students not only need to understand fractions conceptually but also have the ability to apply this understanding in a practical, real-world context, which is essential for demonstrating their learning. This type of objective outlines a clear, actionable task that can be evaluated for student understanding.

The other choices, while they describe activities that may involve student engagement, do not encapsulate the same level of specificity or measurable outcome typical of instructional objectives. Completing a worksheet or finishing homework focus more on the task itself rather than the learning outcome. Participating in a district lacks clarity about what skills or knowledge will be acquired, making it less effective as a clear instructional objective.