**Core Concept**
The spinal cord in children is shorter and ends at a higher level compared to adults, which is crucial for administering neuraxial blocks safely. This anatomical variation is essential for pediatric anesthesia.

**Why the Correct Answer is Right**
In children, the spinal cord ends at the lower border of L3, whereas in adults, it ends at the lower border of L1. This anatomical difference is due to the growth of the vertebral column and the spinal cord. As a result, the dural sac and the spinal canal are relatively shorter in children. For spinal anesthesia, it is essential to administer the anesthetic below the level of the conus medullaris to avoid direct spinal cord injury. In children, the optimal level for spinal anesthesia is below L3, allowing for a safe and effective block.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because the spinal cord does not end at S1 in adults or children. In adults, the spinal cord typically ends at the lower border of L1, while in children, it ends at the lower border of L3.

**Option C:** This statement is incorrect because the dural sac does not extend up to S2 in children. The dural sac typically ends at the lower border of L1 in adults and at the lower border of L3 in children.

**Option D:** This statement is incorrect because the spinal cord does not end at the lower border of L1 in children. In children, the spinal cord ends at the lower border of L3, whereas in adults, it ends at the lower border of L1.

**Clinical Pearl / High-Yield Fact**
When administering spinal anesthesia in children, it is essential to consider their smaller vertebral bodies and shorter spinal cord. The optimal level for spinal anesthesia in children is below L3, and the anesthesiologist must take into account the child's age, size, and weight to ensure a safe and effective block.

**✓ Correct Answer: B. Spinal anaesthesia is given below L3 level in children**