Which immunoglobulin is found in tears, saliva, and breast milk?

The correct choice is IgA, which is primarily found in mucosal areas and secretions such as tears, saliva, and breast milk. IgA plays a crucial role in the immune defense of mucosal surfaces by preventing the attachment and invasion of pathogens. It exists in two subclasses: serum IgA, which is found in the blood, and secretory IgA, which is present in mucosal secretions. The presence of IgA in breast milk is particularly important as it helps provide immunity to infants during breastfeeding, protecting them from infections as their immune systems develop. This specificity of IgA for mucosal immunity highlights its essential function in first-line defense against pathogens encountered through mucosal routes, making it the appropriate answer for this question.