Charging by conduction Steps:

• The metal rod carries positive charge, held by an insulating handle to prevent discharge.
• When the rod contacts uncharged sphere X, electrons flow from X to the rod, leaving X positively charged.
• Sphere Y remains isolated on its insulating stand, unaffected by the contact.
• After separation, X retains the positive charge; Y stays uncharged as initially stated.

Why A is correct:

• Conduction transfers charge between touching conductors until equilibrium, so the positively charged rod induces positive charge on X (like charges repel, electrons leave X).

Why the others are wrong:

• B and C: Y stays positive only if initially charged and untouched, but problem implies Y uncharged; X would gain charge if contacted.
• D: X gains charge from rod contact, so not uncharged.

Final answer: A