A student is using a cathode-ray oscilloscope (c.r.o.) to determine the period of a signal. She adjusts the time-base on the c.r.o. to $5\,\text{ms cm}^{-1}$ and sees the trace shown below. The trace extends over $10.0\,\text{cm}$.\n\nWhat is the period of the signal?
- A$7.1 \times 10^{-6}\,\text{s}$
- B$1.4 \times 10^{-5}\,\text{s}$
- C$7.1 \times 10^{-3}\,\text{s}$
- D$1.4 \times 10^{-2}\,\text{s}$