In the Assessment of Equivocal Results in Pheochromocytoma Testing,the Clonidine

In the assessment of equivocal results in pheochromocytoma testing,the clonidine suppression test is used to differentiate between:

A) elevated blood pressure caused by pheochromocytoma versus that caused by carcinoid tumor.
B) increased serotonin production by the GI tract versus serotonin from the brain.
C) adrenal gland and GI tract increased synthesis of dopamine.
D) adrenal gland and sympathetic nervous system increases in catecholamine synthesis.