Task: Text Categorization
Input (English): Question: Nitric oxide: 
 Options:  <0> It is synthesized from methionine. <1> Activates cAMP-dependent protein kinase (PKA). <2> It binds to receptors coupled to G proteins (GPCR). <3> Induces relaxation of the vascular endothelium. <4> It binds to receptors with protein tyrosine kinase (PTK) activity.
Output (English): chemistry