Task: Question Answering
Input (English): Question: How many macromolecular complexes form the electronic transport chain ?: 
 Options:  <1> 6 macromolecular complexes. <2> 5 macromolecular complexes. <3> 4 macromolecular complexes. <4> 3 macromolecular complexes. <5> 2 macromolecular complexes.
Output (English): 3