The most true statement is:
d. Magicians may know how an illusion is performed, and be able to do it themselves, but that doesn't mean even they can see it when another person does it.
Magicians are experts at misdirection and illusion, and they use these skills to create the appearance of impossible feats. Even when a magician knows how an illusion is performed, they can still be fooled by it if the magician performing it is skilled enough. This is because magicians are not immune to having their attention distracted or overwhelmed, and they can still be fooled by the same tricks that fool the rest of us.
Magicians do not always depend on moving faster than the eyes of the audience can follow. In fact, many illusions are based on slow, deliberate movements that are designed to misdirect the audience's attention. For example, a magician might make a coin disappear by slowly moving it from one hand to the other, while at the same time using their other hand to distract the audience with a flourish or gesture.
Ultimately, the success of a magician depends on their ability to create a sense of wonder and amazement in their audience. If they can do that, then they have succeeded in their job, even if the audience doesn't know exactly how the illusion was performed.