**Core Concept**
The question pertains to the risk of malignancy in cold thyroid nodules, which are a type of thyroid nodule that does not take up radioactive iodine during a thyroid scan. This concept is crucial in distinguishing between benign and malignant thyroid nodules, guiding clinical management and decision-making.

**Why the Correct Answer is Right**
Cold thyroid nodules account for approximately 85% of all thyroid nodules. However, only a small percentage of these nodules are malignant. The risk of malignancy in cold thyroid nodules is generally considered to be low, with most studies suggesting a risk of around 5-10%. The exact risk can vary depending on factors such as the size of the nodule, patient age, and the presence of other risk factors. The malignant potential of cold thyroid nodules is largely due to the presence of follicular or papillary carcinoma.

**Why Each Wrong Option is Incorrect**
**Option A:** 20% - This option is incorrect because the actual risk of malignancy in cold thyroid nodules is significantly lower than 20%.

**Option B:** 50% - This option is incorrect because it overestimates the risk of malignancy in cold thyroid nodules by a substantial margin.

**Option C:** 1% - While closer to the actual risk, this option still underestimates the risk of malignancy in cold thyroid nodules.

**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to remember that the majority of cold thyroid nodules are benign, and a significant proportion of thyroid cancers are not cold on a thyroid scan. This highlights the importance of a thorough clinical evaluation, including fine-needle aspiration cytology (FNAC), to determine the nature of thyroid nodules.

**Correct Answer: D. 5-10%.**