Look at the 2nd decimal place to decide whether to round up or down.
• 12.950: the first decimal place is 9.
• The 2nd decimal digit is 5, which is ≥ 5, so we round up.
• Rounding up from 12.9 gives 13.0 (the 9 becomes 10, carrying 1 to the units).
Final Answer: B: 13.0