chitin

"While walking to school, Sarah found a lost wallet on the ground. "

"Humans share common ancestors with other apes."

"Example Sentence: "Insects, spiders, and crabs are all examples of arthropods, which means they have an external skeleton and jointed legs." "

"The school's computer network is a complex of interconnected systems, linking classrooms, libraries, and administration offices. "

"The old city had strong walls to protect it from enemies. "

"My brother suffers from asthma, which means he sometimes has trouble breathing, especially when he exercises. "

"The responsible for the project is Maria. "

"Idly, the detective thought what his next move should be."

"After the heavy rain, we saw many fungi, like mushrooms and toadstools, growing in the garden. "

"The plastic in my school's new chairs is a polymer. "

"The discarded exoskeletons of cicadas clung to the tree bark in the park. "

"Cellulose, starches, and complex carbohydrates, such as glycogen, are common polysaccharides in biology."