Two students decomposed 90 in different ways. Student A wrote 90=9×10 and obtained 32×2×5. Student B wrote 90=6×15 and obtained 2×3×3×5. Which of the following statements is illustrated by this situation?
a) The prime factorisation of 90 depends on the factor pairs chosen.
b) The prime factorisation of 90 is not unique.
c) The prime factorisation of 90 is unique irrespective of the factor pairs chosen.
d) 90 has exactly two distinct prime factors.