Which statement best differentiates multi-digit addition and subtraction with regrouping from mental math strategies used in elementary grades?

• A. Regrouping involves carrying/borrowing with column arithmetic; mental math strategies are estimation and decomposing numbers without full computation.
• B. Regrouping sometimes uses mental math strategies instead of column methods.
• C. Regrouping is identical to mental math, with no difference.
• D. Regrouping applies only to measuring units, not to addition or subtraction.

Answer: (B)