Which of the Following Is TRUE for Excitation Spectra

Multiple Choice

Which of the following is TRUE for excitation spectra?

A) Excitation wavelength is fixed and the emission wavelengths are scanned.
B) Excitation wavelength is scanned and the emission wavelength is fixed.
C) Excitation wavelength is fixed and the emission wavelength is fixed.
D) Excitation wavelength is scanned and the emission wavelength is scanned.
E) None of these answers is true.