An electric current flows through a copper wire. Which statement about the average drift speed of the charge carriers in the wire is correct?
- AIt is nearly $3 \times 10^8\,\text{m s}^{-1}$.
- BIt is proportional to the cross-sectional area of the wire.
- CIt is proportional to the length of the wire.
- DIt is proportional to the magnitude of the current.