Task: Question Answering
Input (English): Question: The hepatic synthesis of methionine from homocysteine ​​requires: 
 Options:  <1> N5, N10 methenyl-tetrahydrofolate. <2> N10-formyl-tetrahydrofolate. <3> N5-formimino-tetrahydrofolate. <4> N5-methyl-tetrahydrofolate. <5> N5, N10 methylene-tetrahydrofolate.
Output (English): 4