The antibody which can cross placental barrier is

Answer: Option D

Antibodies are like tiny soldiers in your body that fight off infections.
Different types of antibodies have different jobs and abilities.

* IgG (Immunoglobulin G): This is the only type of antibody that can cross the placenta. The placenta is a temporary organ that connects a developing baby to the mother's uterus.
Because IgG can cross the placenta, it provides passive immunity to the fetus (baby) before birth, protecting the baby from infections.

* IgA (Immunoglobulin A): Found mainly in body secretions like tears, saliva, and breast milk. It helps protect surfaces like your airways and digestive system from infections. IgA does *not* cross the placenta.

* IgE (Immunoglobulin E): Involved in allergic reactions and fighting off parasitic infections. IgE does *not* cross the placenta.

* IgM (Immunoglobulin M): The first antibody produced during an infection. It's a big molecule and stays mostly in the bloodstream. IgM does *not* cross the placenta.

So, IgG is special because it can travel from the mother to the baby across the placenta, providing crucial protection during pregnancy.