"Section4.    Exemptions. — The following shall not be taxed under this Act:

(a)    The United States High Commissioner and members of his staff;

(b)    Commissioned officers of the United States Army and Navy;

(c)    Enlisted soldiers, sailors and marines of the United States Army and Navy;

(d)    Civilian officers and employees of the military, naval or any other branch of the United States Government who are not Filipino citizens;

(e)    Diplomatic and consular representatives and officers of foreign powers;

(f)    Transient visitors when their stay in the Philippines does not exceed three months; and

(g)    Barrio lieutenants and their substitutes while holding office as such: Provided, however, That they shall be liable to the payment of the annual additional tax."