(i) We observe that 65 and 84 have no common factor i..e., their HCF is 1.
Thus, is in its lowest form.
(ii) We observe that 15 and 32 have no common factor i..e., their HCF is 1.
Thus, is in its lowest form.
(iii) HCF of 24 and 128 is not 1.
Thus, given rational number is not in its simplest form.
(iv) HCF of 56 and 32 is 8.
Thus, given rational number is not in its simplest form.