A student measures the average speed of a bubble moving up through a liquid at a steady speed. At the moment the student begins the stopwatch, the bubble is at position P. After $2.0\,\text{s}$, the bubble is at position Q. What is the speed of the bubble between P and Q?
- A$3.2\,\text{cm s}^{-1}$
- B$3.7\,\text{cm s}^{-1}$
- C$6.4\,\text{cm s}^{-1}$
- D$7.4\,\text{cm s}^{-1}$