Polyclonal antibodies are described as:

• A. Antibodies produced by injecting animals with a specific antigen; a series of antibodies respond to a variety of sites on the antigen.
• B. Antibodies produced by a single clone of B cells via hybridoma.
• C. Antibodies that bind to the Fc region.
• D. Antibodies produced by plants.

Answer: (A)

Polyclonal antibodies come from an immunized animal and reflect the activity of many different B-cell clones. When the animal is exposed to an antigen, its immune system produces a variety of antibodies, each recognizing a different part (epitope) of the antigen. The resulting preparation is a mixture of antibodies with multiple specificities, rather than a single uniform antibody. This is in contrast to monoclonal antibodies, which come from one B-cell clone and target a single epitope. Antibodies that bind to the Fc region describe a specific binding property, not the source or diversity of the antibodies, and antibodies produced by plants refer to the production system, not the fundamental polyclonal nature. Therefore, the description matches polyclonal antibodies.