Which two test agents are mentioned in relation to the senses of taste?

The correct response highlights the use of Saccharin and Bitrex as test agents pertinent to the study of taste sensations. Saccharin is a well-known artificial sweetener that is often used to test the sweet taste perception, as individuals can discern its sweetness level effectively. Bitrex, on the other hand, is recognized for its extremely bitter taste and is often utilized in taste testing to evaluate bitter receptors. The combination of these two agents allows researchers to explore the full spectrum of taste perception, from sweetness to bitterness, providing valuable insight into how different substances can be recognized and responded to by the human sensory system.

The other options, while mentioning substances that are involved in taste, do not align as closely with distinct taste testing methodologies. For instance, glucose is indeed a sugar that stimulates sweet taste but does not have the same level of application as a test agent like Saccharin does, particularly in a research context for specific taste sensation parameters. Similarly, sodium, although it plays a role in salty taste, does not contribute the same duality of taste testing as Saccharin and Bitrex, which highlight sweet and bitter distinctly.