Which of the following antibodies can detect histone protein expression in a human ovarian tissue using immunofluorescence?

Immunofluorescence works by using two antibodies: a primary antibody that binds directly to the target protein (in this case, histones in human ovarian tissue) and a secondary antibody that is conjugated to a fluorescent dye. The secondary antibody must be specific to the species in which the primary antibody was raised. This ensures that it binds to the primary antibody and produces a detectable fluorescent signal. In this question, the correct pairing is a mouse anti-histone primary antibody with a fluorophore-conjugated horse anti-mouse secondary antibody.