All of the Following Statements Regarding Self- Employment Income/tax Are

All of the following statements regarding self- employment income/tax are true except

A) independent contractors are subject to self- employment tax on the amount of net earnings from the self- employment activity.
B) employees who have a business in addition to their regular employment are not subject to the self- employment tax since FICA is withheld on their wages.
C) the self- employment tax is imposed on net earnings from self- employment when self- employment income is over $400.
D) self- employment tax is computed separately for married individuals filing joint returns.