**Core Concept**
The World Health Organization (WHO) criteria for diagnosing anaemia in infants are age-specific and based on the child's haemoglobin (Hb) levels. These guidelines are crucial for assessing anaemia in infants and guiding appropriate interventions.

**Why the Correct Answer is Right**
The WHO defines anaemia in infants aged 6-11 months as a haemoglobin level less than 110 g/L. This threshold is chosen based on the child's growth and development stages, where a haemoglobin level below 110 g/L indicates a decrease in the infant's ability to carry oxygen to tissues and organs. In infants, the normal haemoglobin range is typically higher than in adults, and the WHO criteria take into account the child's age, sex, and weight.

**Why Each Wrong Option is Incorrect**
**Option A:** 100 gm/litre - This option is too low, as it does not account for the higher haemoglobin levels seen in infants. The normal range for infants is typically between 110-130 g/L.

**Option B:** 105 gm/litre - This option is also incorrect, as it is below the recommended threshold for anaemia in infants aged 6-11 months.

**Option D:** 115 gm/litre - This option is too close to the normal range for infants and does not accurately reflect the WHO criteria for diagnosing anaemia in this age group.

**Clinical Pearl / High-Yield Fact**
It is essential for healthcare providers to be aware of the age-specific WHO criteria for diagnosing anaemia in infants, as these guidelines help ensure accurate diagnosis and appropriate treatment.

**Correct Answer:**
✓ Correct Answer: C. 110 gm/litre