How much should be taken when the instruction is STS?

The instruction STS stands for "swallow this substance," which typically implies a smaller measurement for dosing. In this case, the correct dosage would be 1/2 teaspoon. This amount is commonly used for certain medications and is designed to ensure proper dosing without overwhelming the patient, particularly when dealing with potent substances or liquid medications that are concentrated.

In contrast, the other measurements would likely provide a larger dose than intended in this context. For example, 1 tablespoon is equivalent to three teaspoons and could lead to excessive dosing. A full teaspoon also provides a larger dose than what might be recommended, especially for children or sensitive populations. A flat teaspoon could still imply a slightly larger dose than intended since it suggests a level instead of a measured flat amount that could be less potent. Therefore, 1/2 teaspoon aligns with safer and more precise dosing guidelines.