Which of the following best defines Western blotting (immunoblotting)?

A cell culture assay that measures cytopathic effects of pathogens on living cells over time and then confirms infection by staining intact cells with general protein dyes.

A laboratory method that separates proteins by gel electrophoresis and then detects specific proteins using labeled antibodies applied to a transferred membrane.

A technique that amplifies DNA sequences using cyclic temperature changes followed by detection with sequence-specific probes and fluorescent dyes, typically used for nucleic acid assays in clinical microbiology.

A mass spectrometry-based method that digests proteins, separates peptides by mass to charge ratio, and identifies them by matching spectra to databases without using antibodies at any step.