Final answer:
Both heavy and light chains are indeed necessary for an antibody to bind an antigen, as they form the antigen-binding sites together.
Step-by-step explanation:
The statement that both the heavy and light chains are needed to bind an antigen is true. Antibodies are glycoproteins that consist of two heavy chains and two light chains. The antigen-binding sites of an antibody are formed by the variable regions of both the heavy and the light chains working together. The light chains significantly contribute to the specificity of these sites, allowing the antibody to recognize and bind to specific antigens. This is essential for the immune system's ability to target and neutralize pathogens effectively.