Task: Question Answering
Input (English): Question: The papillary muscles: 
 Options:  <1> They contract atrio-ventricular valves. <2> They prevent the reflux of blood to the atria. <3> They avoid the eversion of the semilunar valves. <4> They form the interventricular septum. <5> They are formed by visceral smooth muscle.
Output (English): 2