An axon can range in length from a fraction of an inch to:

• A. no more than 5 inches
• B. over a meter
• C. about 10 centimeters
• D. exactly 1 foot

Answer: (B)

Verified step by step guidance

1. Understand the context: An axon is a part of a neuron, which is a specialized cell in the nervous system. Axons are responsible for transmitting electrical signals from the cell body to other neurons, muscles, or glands. Their length can vary depending on the type of neuron and its function.
2. Recall the biological fact: Some axons, particularly those in large animals or humans, can be extremely long. For example, the axons of motor neurons that extend from the spinal cord to the toes can be over a meter in length.
3. Eliminate incorrect options: Review the provided options and eliminate those that are biologically implausible. For instance, 'no more than 5 inches' and 'exactly 1 foot' are too short for certain axons, such as those in the human body that extend to the extremities.
4. Compare plausible options: Between 'about 10 centimeters' and 'over a meter,' consider which is more accurate for the longest axons. Axons in the human body, such as the sciatic nerve axon, can exceed a meter in length.
5. Conclude the correct answer: Based on the biological understanding of axon lengths, the correct answer is 'over a meter.' This reflects the maximum length of certain axons in the human body.