Final answer:
The distance between two consecutive points that are in phase on a wave, such as from crest to crest or trough to trough, can be measured to determine one wavelength. Therefore, if the points C and E or C and A are points of similar position in a wave diagram, they would be suitable for measuring a single wavelength.
Step-by-step explanation:
To measure one wavelength on a wave, you would look for two consecutive points where the wave is in the same position. For example, you might measure from one crest to the next crest or from one trough to the next trough. These points are also known as being 'in phase.' This is visually represented in Figures 8.10 and 12.9, which illustrate that the wavelength of a single wave is the distance between two consecutive points of similar position along the wave.
In addressing the student's question, if we are given specific points labeled on a diagram, such as C and E or C and A (assuming these are points depicting similar positions, like trough to trough or crest to crest), these would be the two points between which the distance should be measured to find one wavelength.
Therefore, if the points C and E or C and A are points of similar position in a wave diagram, they would be suitable for measuring a single wavelength.