<prompt> Which of the following conversion is irreversibleFormyl THFA to Methenyl-THFAMethenyl THFA to Methylene-THFAMethylene THFA to Methyl-THFAAll of the above  <response>: One carbon groups are formed from various sources. Except the formation of methyl-THFA The other one-carbons are interconveible The only way of regeneration of active THFA from methyl-THFA is the methionine synthase reaction. 