Final answer:
Tears are part of the body's first line of defense and are a non-specific chemical barrier that help protect against pathogens. They fall under the category of the innate immune system's nonspecific defenses, which makes the correct answer to the student's question option b. 1, 5.
Step-by-step explanation:
Tears are considered to be part of the body's first line of defense. Specifically, they are part of the innate immune system's non-specific defenses. This means that tears act as a chemical barrier to pathogens regardless of the type of the invading agent. The role of tears is to wash away foreign particles and pathogens from the eye, thereby preventing infections. The first line of defense consists of physical, chemical, and biological barriers that are always ready to defend the body from infection. Given these functions, tears can be categorized as part of the 1. first line of defense and the 5. nonspecific defenses.
The human body uses chemical barriers, such as the enzymes found in tears, mucus, and stomach acid, to destroy pathogens before they can enter the body tissues. These barriers are not tailored to a specific pathogen but are ready to act against a wide range of invaders. Therefore, the correct answer to the question is option b. 1, 5, meaning that tears are part of the first line of defense and are a nonspecific defense mechanism.