Task: Question Answering
Input (English): Question: Gas chromatography combined with mass spectrometry (GC-MS) is the most commonly used chromatographic coupled technique. The main difficulty of the coupling is in: 
 Options:  <1> The analysis of molecular ions in the same place where they are generated. <2> The production of highly fragmented ions with accelerated electron generation. <3> The increase in the output flow rate of the chromatograph, which can not exceed nL / min. <4> The obtaining of the bidimensional spectrum that allows the separation in function of the relationship q / r. <5> The introduction into the high vacuum of the mass analyzer, of a compound that is at an atomospheric pressure.
Output (English): 5