The time-base of a cathode-ray oscilloscope is adjusted to $6\,\text{ms}\,\text{cm}^{-1}$. A trace containing two pulses is shown in the diagram. What is the time interval separating the two pulses?
- A$0.42\,\text{ms}$
- B$0.75\,\text{ms}$
- C$1.33\,\text{ms}$
- D$27\,\text{ms}$