**Core Concept**
Double-blinding refers to a research design where both the participants (subjects) and the researchers (investigators) are unaware of the treatment being administered. This type of blinding is essential in clinical trials to minimize bias and ensure the validity of the results.

**Why the Correct Answer is Right**
Double-blinding is achieved when both the participants and the researchers are blinded to the treatment allocation. This can be done by using placebos or identical-looking active treatments. For instance, in a double-blind study, the researchers may administer a medication to the participants, while the participants are given a placebo or vice versa. The researchers may also be given a code or a sealed envelope that indicates the treatment allocation, but they do not know which treatment is being administered to each participant. This blinding technique helps to prevent bias and ensures that the results are not influenced by the researcher's expectations or the participant's knowledge of the treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** Single-blinding refers to a research design where only one group (either the participants or the researchers) is aware of the treatment being administered. This is not the type of blinding mentioned in the question.

**Option B:** Triple-blinding is a research design where three groups are blinded: the participants, the researchers, and the data analysts. While triple-blinding is a more rigorous approach, it is not the type of blinding mentioned in the question.

**Option D:** Unblinding refers to the process of revealing the treatment allocation to either the participants or the researchers. This is the opposite of what is described in the question.

**Clinical Pearl / High-Yield Fact**
In clinical trials, blinding is essential to minimize bias and ensure the validity of the results. Double-blinding is a more rigorous approach than single-blinding, and it is often used in trials where the treatment effect is expected to be small.

**Correct Answer: C. Double-blinding**