Final answer:
To assess the capability of solar energy power to be pollution-free, one must consider all aspects impacting the environment. Among the given options, observing that the ground outside a manufacturing plant has changed does not directly inform on the pollution-free nature of solar cells, as it does not relate to the solar cell's production or its generation of electricity.
Step-by-step explanation:
To determine which method does not help in judging whether solar energy power can be pollution-free, we can evaluate the options provided. Option A, calculating the cost to make a solar cell, can be somewhat related to the pollution aspect since higher costs might suggest more resource-intensive and potentially polluting processes; however, it is not a direct measure of pollution. Option B, observing a cell making electricity in your hand, is a direct encounter with the technology, but it does not inform on the pollution created during the manufacturing process or the operation of the entire solar system. Option C, measuring the amount of electricity needed to make a solar cell, is directly related to the pollution potential, as the energy source for manufacturing could be polluting. Option D, observing that the ground outside one manufacturing plant turned, is the one that does not directly relate to the function of the solar cell or the amount of pollution its production and operation may generate.