Answer : The object reflects light with the longest wavelength is, A yellow book.
Explanation :
When a white light is passing through a prism then the white light separated into different colors with different wavelength.
The different visible colors from shortest to longest wavelength are, violet, blue, green, yellow, orange, red.
That means violet has shortest wavelength and red has longest wavelength.
As per given in the question, a yellow book object reflects light with the longest wavelength.
Hence, the correct option is, A yellow book.