What should be used firmly to examine the mouth effectively?

To effectively examine the mouth, a tongue blade is essential. A tongue blade, or tongue depressor, is designed specifically to allow for a clear view of the oral cavity by holding the tongue down and out of the way. This instrument is both firm enough to provide control while also being smooth, ensuring patient comfort. By depressing the tongue, the clinician can better visualize the soft palate, oropharynx, and other structures of the mouth without obstruction.

In contrast, other options are not suitable for this specific purpose. A toe separator is unrelated to oral examinations, as it is designed for pedicure or podiatric use. A mirror, while helpful for reflecting images and aiding visibility, is not used to directly manipulate or inspect the oral structures themselves. An "inspected tool" is vague and does not specify an instrument designed for oral examination. The precision and functionality of the tongue blade make it the best choice for examining the mouth effectively.