From the following, what charges can be present on oil drops in Millikan's experiment ?

Which of the following charge (s) can exist on an oil drop (in Millikan's oil drop experiment)

Which of the following charge (s) can exist on an oil drop (in Millikan's oil drop experiment)

Which of the following forces act on oil drops in Millikan's experiment?

What type of oil should be used in Millikan's oil drop experiment ?

What important fact did Millikan's experiment establish ?

If g_E and g_M are the acceleration due to gravity on the surfaces of the earth and the moon respectively and if Millikan's oil drop experiment could be performed on the two surfaces, one will find the ratio electronic charge on the moon/electronic charge on the earth to be