The diagram illustrates a cathode-ray oscilloscope (c.r.o.) being used to determine the rotation rate of a flywheel. A small magnet is fixed to the flywheel. Whenever the magnet goes past the coil, a voltage pulse is produced and sent to the c.r.o. The screen of the c.r.o. is $10\,\text{cm}$ across. The flywheel is turning at approximately $3000$ revolutions per minute. Which time-base setting would show the pulses as clearly separated on the screen?
- A$1\,\text{s cm}^{-1}$
- B$10\,\text{ms cm}^{-1}$
- C$100\,\text{\mu s cm}^{-1}$
- D$1\,\text{\mu s cm}^{-1}$