The correct answer is: B. 31
There are 31 pairs of spinal nerves in humans. These nerves emerge from the spinal cord and extend to various parts of the body. They carry both sensory and motor information.
The spinal nerves are divided into eight cervical nerves, twelve thoracic nerves, five lumbar nerves, five sacral nerves, and one coccygeal nerve. The cervical nerves supply the neck and upper limbs. The thoracic nerves supply the chest and abdomen. The lumbar nerves supply the lower back and lower limbs. The sacral nerves supply the pelvis and lower limbs. The coccygeal nerve supplies the coccyx.
Each spinal nerve is formed by the union of a dorsal root and a ventral root. The dorsal root carries sensory information from the body to the spinal cord. The ventral root carries motor information from the spinal cord to the body.
The spinal nerves are important for controlling movement, sensation, and reflexes. They also play a role in autonomic functions such as breathing and heart rate.
Here is a brief explanation of each option:
- Option A: 30. This is incorrect because there are 31 pairs of spinal nerves in humans.
- Option B: 31. This is the correct answer because there are 31 pairs of spinal nerves in humans.
- Option C: 32. This is incorrect because there are 31 pairs of spinal nerves in humans.
- Option D: 33. This is incorrect because there are 31 pairs of spinal nerves in humans.