下列那一種物質是正腎上腺素(norepinephrine)的主要代謝產物？
homovanillic acid (HVA)
5-hydroxyindoleacetic acid (5-HIAA)
3-methoxy-4-hydroxyphenylglycol (MHPG)
3,4-dihydroxyphenylacetic acid (DOPAC)
