Comets do not give off their own light but reflect light from other sources, such as the Sun. Scientists estimate the mass of comets by their brightness: the greater a comet' s mass, the more light that comet will reflect. A satellite probe, however, has revealed that the material of which Halley' s comet is composed reflects 60 times less light per unit of mass than had been previously thought. The statements above, if true, give the most support to which one of the following? ['The reflective properties of the material of which comets are composed vary considerably from comet to comet.', "Previous estimates of the mass of Halley's comet which were based on its brightness were too low.", "The total amount of light reflected from Halley's comet is less than scientists had previously thought.", "Scientists need more information before they can make a good estimate of the mass of Halley's comet."]