The absorption curve is ( ). A: The curve of the relationship between the concentration of light-absorbing substance and absorbance. B: The curve of the relationship between the concentration of light-absorbing substance and transmittance. C: The curve of the relationship between the wavelength of incident light and the thickness of light-absorbing substance solution. D: The curve of the relationship between the wavelength of incident light and the absorbance of a light-absorbing substance.

What type of technique is FTIR spectroscopy? ( ) A: A dispersive technique B: An emission technique C: An absorbance technique D: A UV-Vis technique E: A reflectance technique