If a5 ≤ a, which of the following must be true?

I -1 ≤ a ≤ 0

II a=0

III 0 ≤ a ≤ 1

a. None of the above
b. I only
c. II only
d. III only
e. I and III only


Source : Master GMAT Test
Answer given: A (None of the above)