Final answer:
A measurable objective for reducing mouth injuries in health class is for students to demonstrate the proper fitting and use of a mouthguard. This objective is observable and assessable, covering both understanding and practical application crucial for effective injury prevention.
Step-by-step explanation:
The more measurable objective for a teacher's plan to reduce sports-related mouth injuries in health class is option 3: The student will demonstrate proper fitting and use of a mouthguard. This objective is directly observable and can be assessed by the teacher, thereby providing clear evidence that the student has acquired the skill. A demonstration involves both knowledge and practical application, which covers understanding the importance of mouthguards (option 1) and identifying different types (option 2). This ensures that the students not only learn about the different mouthguards but also how to use them effectively, which is essential for injury prevention.
Option 4, regarding regular dental check-ups, is also important for overall oral health, but it is less directly related to the immediate goal of preventing injuries during sports activities and more difficult to measure in the classroom setting. Overall, an objective that involves students actively demonstrating a skill provides clear, actionable outcomes for the teachers to measure and is most aligned with the goals of a health education class focused on preventing injuries.