The resistivity of iron is $1 \times 10^{-7} \, \Omega \cdot m$. The resistance of an iron wire of a particular length and thickness is $1 \, \Omega$. If the length and the diameter of the wire are both doubled, then the resistivity in $\Omega \cdot m$ will be:

• A
  $1 \times 10^{-7}$
• B
  $2 \times 10^{-7}$
• C
  $4 \times 10^{-7}$
• D
  $8 \times 10^{-7}$