**Core Concept**
Anganwadi workers under the Integrated Child Development Services (ICDS) program use growth charts to monitor the growth and development of children. These charts are specifically designed to track the health and nutritional status of children from birth to 5 years of age.

**Why the Correct Answer is Right**
The growth charts used by Anganwadi workers are typically the World Health Organization (WHO) growth charts, which are widely recognized and accepted for monitoring growth and development in children. These charts take into account the growth patterns of children from different regions and populations, allowing for more accurate assessments. The WHO growth charts are specifically designed for use in low- and middle-income countries, making them a suitable choice for ICDS programs.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as there is no widely recognized growth chart by this name.
**Option B:** This option is incorrect as the National Family Health Survey (NFHS) growth charts are used for research purposes, not for routine growth monitoring in ICDS programs.
**Option C:** This option is incorrect as the growth charts developed by the Indian Academy of Pediatrics (IAP) are used for clinical purposes, not for growth monitoring in ICDS programs.

**Clinical Pearl / High-Yield Fact**
Anganwadi workers should be trained to use the WHO growth charts correctly, as these charts are specifically designed to track growth and development in children from different regions and populations.

**Correct Answer: D. WHO growth charts.**