On a sunny day, the sky overhead appears blue because air molecules scatter shorter wavelengths of sunlight more than longer ones. The same physics, however, predicts that the sky should look more violet than blue, since violet light is scattered even more strongly. The reason it does not is that human eyes are far less sensitive to violet than to blue.
Which choice best describes the function of the second sentence in the text?
- A
It defines the term 'wavelength'.
- B
It refutes the physics of light scattering.
- Ccheck_circle
It introduces a tension between the explanation and ordinary observation that the third sentence resolves.
- D
It supports the explanation introduced in the first sentence.
Explanation
The second sentence raises a puzzle ("should look violet") that the third sentence then resolves. B captures this setup function.