The resistivity of a metal is $1 \times 10^{-8} \Omega \cdot m$. If it contains $9 \times 10^{28}$ electrons per $m^3$, then the relaxation time of electrons inside the metal is nearly (electron mass $= 9 \times 10^{-31} \ kg$).

  • A
    $4 \times 10^{-14} \ s$
  • B
    $7 \times 10^{-14} \ s$
  • C
    $1.0 \times 10^{-14} \ s$
  • D
    $9 \times 10^{-14} \ s$

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