A $12\,\text{V}$ lamp shines at its normal brightness when it is connected to the secondary winding of a mains transformer. The mains voltage is $240\,\text{V}$. The transformer has an efficiency of $100\%$ and the primary winding contains $200$ turns. How many turns does the secondary winding have?
- A$10$
- B$14$
- C$4000$
- D$580\,000$