Final answer:
Selenocysteine, like cysteine, is sp³d hybridized and therefore has 4 sp hybrid orbitals.
Step-by-step explanation:
Selenocysteine is an amino acid that contains an seleno group (-SeH) instead of the sulfur group (-SH) found in cysteine. Since selenium is in the same group as sulfur in the periodic table, it has similar hybridization properties. Sulfur in cysteine is sp³d hybridized, meaning it forms four sp³d hybrid orbitals for bonding. Similarly, selenium in selenocysteine will also be sp³d hybridized. Therefore, the correct answer is D. 4.