The graph shows how the current in a lamp filament changes with potential difference (p.d.). Which statement explains the shape of this graph?
- AAs the filament temperature rises, electrons can pass more easily through the filament.
- BIt takes time for the filament to reach its working temperature.
- CThe power output of the filament is proportional to the square of the current in it.
- DThe resistance of the filament increases with a rise in temperature.