Red Blood Cell Structure

Steps:

• Red blood cells are animal cells, which lack rigid cell walls unlike plant cells.
• Mature mammalian red blood cells lose their nucleus during development to maximize space for oxygen transport.
• Thus, they have a flexible plasma membrane but no cell wall or nucleus.
• This matches option A as the defining features.

Why A is correct:

• Mature red blood cells are anucleate and lack a cell wall, per standard cell biology definitions of animal cell structure.

Why the others are wrong:

• B: Animal cells like red blood cells do not have a cell wall; that's a plant cell feature.
• C: Mature red blood cells lack a nucleus, which is extruded for efficient hemoglobin packing.
• D: Red blood cells have neither a cell wall nor a nucleus.

Final answer: A