**Core Concept**
Weight for height is an important anthropometric parameter used to assess the nutritional status of a child. It is a sensitive indicator of acute or chronic malnutrition. A deficit in weight for height suggests that the child's weight is less than expected for their height, indicating a loss of muscle mass, body fat, or both.

**Why the Correct Answer is Right**
Deficit in weight for height is primarily due to an imbalance between energy intake and expenditure, leading to a negative energy balance. This can be caused by inadequate nutrition, increased energy expenditure due to illness, or a combination of both. In a 3-year-old child, a deficit in weight for height can indicate acute malnutrition, which can be life-threatening if left untreated.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because stunting is a result of chronic malnutrition, which is reflected in a low height for age, not a deficit in weight for height.

**Option B:** This option is incorrect because wasting is a result of acute malnutrition, which is reflected in a low weight for height, but it is not the same as a deficit in weight for height. Wasting is a more severe form of malnutrition.

**Option C:** This option is incorrect because this term is not relevant to the anthropometric parameters used to assess nutritional status in children.

**Clinical Pearl / High-Yield Fact**
When assessing the nutritional status of a child, it's essential to consider the height-for-age, weight-for-height, and weight-for-age parameters to differentiate between acute and chronic malnutrition.

**Correct Answer:** B. Wasting.