Which of the above are optical illusions?

Consider the following phenomena:

1. Size of the sun at dusk

2. Colour of the sun at dawn

3. Moon being visible at dawn

4. Twinkle of stars in the sky

5. Polestar being visible in the sky

Which of the above are optical illusions?(2013)

a) 1, 2 and 3

b) 3, 4 and 5

c) 1, 2 and 4

d) 2, 3 and 5

ANswer: C