Which sequence of actions will leave a neutral conducting sphere with a net positive charge after all objects are removed?
a) Bring a positively charged rod near the sphere, connect the sphere to ground, disconnect the ground while the rod is still present, then remove the rod
b) Bring a negatively charged rod near the sphere, connect the sphere to ground, remove the rod while the ground wire is still attached, then disconnect the ground
c) Bring a negatively charged rod near the sphere, connect the sphere to ground, disconnect the ground while the rod is still present, then remove the rod
d) Bring a negatively charged rod near the sphere and, without grounding the sphere, simply remove the rod