What is the source of gravity at the heart of many galaxies? a. dark matter

b. fusion

c. black holes

d. neutrinos

When is a current produced? when the terminals of an electrochemical cell are connected by a wire if the electric circuit is opened in an electrochemical cell if the electrolyte is removed from an electrochemical cell when the electrodes are reversed in an electrochemical cell

Awave has a wavelength of 7 mm and a frequency of 19 hertz. what is its speed?

Atoms containing radioactive nuclei are called