Answer:
(d) [tex]\sf \textsf{C}_6\textsf{D}_6 [/tex]
Explanation:
When benzene is heated in a large excess of 80% [tex]\sf \textsf{D}_2\textsf{SO}_4 [/tex] in [tex]\sf \textsf{D}_2\textsf{O} [/tex] (deuterium oxide, heavy water), it undergoes electrophilic aromatic substitution with deuterium replacing a hydrogen atom.
The product formed is deuterated benzene, also known as deuterium or [tex]\sf \textsf{C}_6\textsf{D}_6 [/tex].
Therefore, the correct option is:
(d) [tex]\sf \textsf{C}_6\textsf{D}_6 [/tex]
