Pluto was first observed in 1930, and its largest moon, charon, was discovered in 1978. a few years after charon’s discovery, astronomers were able to observe a series of eclipses as pluto and charon passed in front of one another. by studying how the brightness of pluto and charon changed as they eclipsed each other, astronomers were able to measure the masses and radii of both pluto and its moon. what did these measurements imply about the average densities of pluto and charon?

a. pluto and charon have average densities that are expected for objects made mostly of water ice.
b. pluto and charon have average densities that are expected for objects made of rock.
c. pluto and charon have average densities that are expected for objects made mostly of gas.
d. pluto and charon have average densities that are expected for objects made mostly of liquid.