Task: Question Answering
Input (English): Question: The loss of linearity of the calibration line when the fluorescence intensity is used as an analytical parameter may be due to: 
 Options:  <1> Changes in solvent density as the concentration of fluorescent analyte increases. <2> Dissolved oxygen, due to its diamagnetic character, which favors intersystem crossing. <3> The presence of static inhibitors of the incident radiation. <4> Internal conversion, in which the energy absorbed can be transformed into heat energy. <5> Self-absorption, to the internal effect of bucket and to the formation of dimers and excimers.
Output (English): 5