To solve this problem, we need to identify which function is not performed by the secretions from salivary glands. Let's analyze each option:$\newline \bullet$Option 1: Control bacterial population in the mouth$\newline$ - Saliva contains lysozyme and other antimicrobial agents that help control bacterial growth.$\newline$ - Therefore, this function is performed by salivary secretions.$\newline \bullet$Option 2: Digestion of complex carbohydrates$\newline$ - Saliva contains the enzyme amylase, which begins the digestion of complex carbohydrates like starch into simpler sugars.$\newline$ - Thus, this function is performed by salivary secretions.$\newline \bullet$Option 3: Lubrication of oral cavity$\newline$ - Saliva provides lubrication to the oral cavity, aiding in speech and swallowing.$\newline$ - Hence, this function is performed by salivary secretions.$\newline \bullet$Option 4: Digestion of disaccharides$\newline$ - Saliva does not contain enzymes that digest disaccharides. Disaccharide digestion occurs primarily in the small intestine.$\newline$ - Therefore, this function is not performed by salivary secretions.$\newline$Based on the analysis, the correct answer is Option 4: Digestion of disaccharides.