Sea stars possess strands of tissue that encircle the mouth and run into the arms; these strands of tissue make up the ( ) system. A: hemal B: secretory C: skeletal D: muscular E: excretory

Which of the following is NOT true of the alveolar sac A: Directly communicates with the alveolar duct B: Has an interrupted wall represented by knobs between adjacent alveoli C: The space surrounded and opened by many alveoli D: Connective tissue fibers encircle the openings of the alveoli E: Smooth muscle disappears in this segment

Which of the following is NOT true of the alveolar sac() A: Directly communicates with the alveolar duct B: Has an interrupted wall represented by knobs between adjacent<br/>alveoli C: The space surrounded and opened by many alveoli D: Connective tissue fibers encircle the openings of the alveoli E: Smooth muscle disappears in this segment