A current-carrying wire is known to produce magnetic lines of force around the conducting straight wire. The direction of the lines of force may be described by

• A. Left-hand thumb rule for up-current and right-hand thumb rule for down-current.
• B. Right-hand thumb rule for up-current and left-hand thumb rule for down-current.
• C. Right-hand thumb rule for both up and down currents.
• D. Left-hand thumb rule for both up and down currents.