As you know that (D,/) is a POSET (partially ordered set) if it fulfills three properties of,

Reflexivity

Antisymmetric

Transitivity

In addition to these, if all elements in your set also are comparable with each other.all element in a set are comparable with respect to division operator then POSET is TOSET.

Option A ALL element are comparable with respect to division operator ( 6 divided by 2,24 divided by 6 and 2).

option B Here 3,5 are not comparable (5 not divide by 3 or 3 not divide by 5)

option C Here (2,9 ),(16,9) are not comparable (9 not divide by 2 or 16 not divide by 9)

option D Here (4,15),(4,30) are not comparable (15 not divide by 4 or 30 not divide by 4)