The unit of measurment should be check again and again why

The charge on a charged sphere is: a)concentrated at its centerb)distributed uniformly throughout its volumec)clustered on its centerd)distributed uniformly over its surface

There are two-speed cameras, one in an are where the speed limit is 30 km/h and another where the speed limit is 50 km/h. in which will there be a smaller time interval between the photographs? explain your answer.

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2