Nicholas has been diagnosed with Parkinson's disease. We can expect that Nicholas will

a) have difficulty moving, but his emotional expression will be normal.
b) be able to smile spontaneously when he hears a good joke, but not when a photographer asks him to do so.
c) be able to smile voluntarily for a photograph, but will not smile spontaneously when he hears a good joke.
d) show little to no emotional expression at all.