The compound used in the treatment of lead poisoning is:

We start by recalling a basic fact from medicinal chemistry: heavy-metal poisoning is commonly treated by administering chelating agents, that is, ligands that form stable, soluble complexes with the toxic metal ion and thus help the body excrete it.

Now, for lead ( $$\text{Pb}^{2+}$$ ) poisoning, the standard chelating agent is ethylene-diamine-tetra-acetic acid, abbreviated as $$\text{EDTA}$$. The four carboxylate groups (-COO−) and the two -NH- groups present in EDTA act together to donate lone pairs and wrap around the lead ion, forming a hexadentate chelate ring. This reaction can be represented symbolically as

$$ \text{Pb}^{2+} + \text{H}_2\text{EDTA}^{2-} \;\longrightarrow\; [\text{PbEDTA}]^{2-} + 2\,\text{H}^+ $$

This complex, $$[\text{PbEDTA}]^{2-}$$, is highly water-soluble and biologically inert, so it can be filtered by the kidneys and removed from the bloodstream.

Next, we briefly examine the other options to confirm they are not preferred for lead:

Desferrioxime B is selective for excess iron (Fe), Cis-platin is an antitumor drug containing platinum, and D-penicillamine is more effective against copper (Cu) poisoning such as in Wilson’s disease. None of these form a chelate with lead as efficiently as EDTA does.

Therefore, among the given choices, the compound actually used in the treatment of lead poisoning is $$\text{EDTA}$$, corresponding to Option B (option 2 in numeric order).

Hence, the correct answer is Option B.