Final answer:
Ubiquitination targeting proteins for proteasomal degradation typically involves polyubiquitination at Lysine 48. Therefore, the correct answer is A. Lysine 48; Polyubiquitination.
Step-by-step explanation:
The question relates to the process of ubiquitination, particularly the addition of ubiquitin molecules to a lysine residue on a protein for the purpose of tagging it for degradation, typically through the action of the proteasome. For lysosomal degradation, the specific type of ubiquitination involved is the attachment of multiple ubiquitin molecules, known as polyubiquitination, to a lysine residue. While several lysine residues can be ubiquitinated, the specific one associated with targeting proteins to the proteasome for degradation is Lysine 48 through polyubiquitination. Therefore, the correct answer is A. Lysine 48; Polyubiquitination.