Which of the following best describes the rule for determining the number of significant figures when using a measuring instrument?

• A. Record all digits, including those you cannot see.
• B. Record only the digits that are marked on the instrument.
• C. Record all certain digits plus one estimated digit.
• D. Record only one digit, regardless of the instrument's precision.

Answer: (C)

Verified step by step guidance

1. Understand that significant figures in measurements reflect the precision of the measuring instrument.
2. Recognize that all digits that are certain (clearly marked or read from the instrument) must be recorded.
3. Include one additional digit that is estimated or uncertain, which represents the limit of the instrument's precision.
4. This rule ensures that the measurement reflects both the exact readings and the uncertainty inherent in the measurement process.
5. Therefore, the correct approach is to record all certain digits plus one estimated digit to properly represent the measurement's precision.