A wire of length $l$ has a resistance $R$. If half of the length is stretched to make the radius half of its original value, then the final resistance of the wire is



 

• A

  $9R$
• B

  $5R$
• Correct answer
  C

  $\frac{17R}{2}$
• D

  $3R$

Hence, the correct answer is option: 'C'.