1 Choose the correct options. 1 don't understand / am not understanding how optical
illusions work; they involve too much science.
2 Optical illusions play are playing tricks both on the
brain and the vision.
3 Since the 19th century, scientists have learnt Khave
been learning more and more about optical illusions.
4 Karen believes / is believing she can come up with a
new optical illusion.
5 Looking at this optical illusion, it seems /Cis seeming to
(me that the circles are rotating.
6 Right now, my uncle shows/ is showing me how
different optical illusions work / are working.