Answer:
in the past, young artists would study with a master artist to learn from him. They would copy his art in an attempt to gain his skill and wisdom and he was right there guiding them. Art historians are often able to identify these copies, but not always. As a result, there’s sometimes the risk that a collector will purchase an art piece attributed to a master when it was, in fact, his student’s work.
Answer:
perspective drawing, emotive drawing
sculptures: you create them by hand, they are physical
photographs: you capture them in electronics, they can't be touched
both: both pieces of art