Final answer:
A tongue blade is used to avoid triggering the gag reflex during an oral cavity exam, which provides a clear view of the throat and tests for cranial nerve function.
Step-by-step explanation:
The nurse uses a tongue blade placed to the side of the child's tongue to examine the child's throat to avoid the problem of triggering the gag reflex. The tongue blade, also known as a tongue depressor, helps to gently lower the tongue without causing discomfort or reflexive gagging, which can interfere with the visual inspection of the throat. By placing the blade to the side, the nurse can have an unobstructed view of the throat, fauces, and any signs of infection such as in tonsillitis or to test the function of cranial nerves associated with the oral cavity.