The diameter of a toroid is 22 cm. It has a cross-sectional area of 0.500 cm². Determine the number of turns required to make the inductance of the toroid 0.200 mH.  

• A. 1.48 × 10³ turns
• B. 2.2 × 10⁶ turns
• C. 4.7 × 10³ turns
• D. 2.1 × 10³ turns

Answer: (A)