Which among the following pairs has only herbicides?

We need to identify the pair in which both substances are herbicides (chemicals used to kill unwanted plants/weeds).

We recall the classification of common pesticides. Aldrin and Dieldrin are well-known insecticides — they belong to the class of chlorinated hydrocarbon insecticides used to kill insects, not weeds.

On the other hand, sodium chlorate ($$NaClO_3$$) and sodium arsenite ($$Na_3AsO_3$$) are both classified as herbicides. Sodium chlorate is a non-selective herbicide that kills plants by oxidative damage, and sodium arsenite has historically been used as a weed killer.

Now let us examine the other options. Option B pairs sodium chlorate (herbicide) with Aldrin (insecticide) — not both herbicides. Option C pairs sodium arsenite (herbicide, noting the question writes "arsinate" but means arsenite) with Dieldrin (insecticide) — again, not both herbicides.

Hence, the only pair where both substances are herbicides is sodium chlorate and sodium arsenite.

Hence, the correct answer is Option D: Sodium chlorate and sodium arsenite.