Lassaigne's test is used for detection of:

In organic compounds, elements such as nitrogen, sulphur, and halogens are covalently bonded to carbon and cannot be detected directly by ordinary inorganic qualitative tests.

Lassaigne's test involves fusing the organic compound with metallic sodium. During fusion, these covalently bonded elements are converted into water-soluble ionic sodium salts, which can then be identified by standard chemical tests.

Nitrogen is converted into sodium cyanide, $$NaCN$$

Sulphur is converted into sodium sulphide, $$Na_2S$$

Halogens $$(Cl,\ Br,\ I)$$ are converted into sodium halides, $$NaX$$

If both nitrogen and sulphur are present in the compound, they combine with sodium and carbon during fusion to form sodium thiocyanate, $$NaSCN$$

Thus, Lassaigne's test is specifically used for the detection of nitrogen, sulphur, and halogens by converting them into ionic sodium salts.

Therefore, the correct answer is $$\text{Nitrogen, Sulphur and Halogens}$$, thus the right option is D.