For which pair of objects would adding the same amount of electrons to each object result in a decrease in the electric force?

two positively charged oljects
two negatively charged objects
two objects that have no charge
two objects that have opposite charges

This is the number of complete movements of a wave per second.

What would people living along the coast in south florida do if there was a hurricane warning? move to locations away from the water flock along coasts to watch the natural phenomenon buy instruments to predict the exact location of the hurricane measure water levels to know the exact time of the hurricane

What would be the radius of the earth if it had its actual mass but had the density of nuclei? express your answer to two significant figures and include the appropriate units.