Answer:
a) The work done on the particle has a positive sign.
Explanation:
When a positive charge is placed in a electric field , a force is exerted by electric field along the direction of the electric field . But the external force is acting on it so that displacement is opposite to the field . That means the external force is acting opposite to electric force on the charged particle.
The displacement is along the external force applied so both force and displacement are positive . Hence work done is positive .
Work done by electric field is negative , because displacement and electric force are opposite.