Three Charges Are Brought from Infinity and Placed at the Corner

Three charges are brought from infinity and placed at the corner of an equilateral triangle.Which of the following statements is true?

A) The work required to assemble the charges is always positive.
B) The electrostatic potential energy of the system is always positive.
C) The electrostatic potential energy does not depend on the order the charges are placed at the corners.
D) The work required to assemble the charges depends on which charge is placed at which corner.
E) The electrostatic potential energy depends on which charge is placed at which corner.