The phrase "vocal... exponent" (line 2, paragraph 5) most probably refers to______.

A．a low-salt diet may be prescribed for some people
B．the amount of salt intake has nothing to do with one's blood pressure
C．the reduction of salt intake can cure a hypertensive patient
D．an extremely low-salt diet makes no difference to anyone

A．exhibits as an aggravating factor to people in poor health
B．cures diseases such as stroke and circulatory disorders
C．correlates highly with some diseases
D．is irrelevant to people suffering from heart disease