20. The function of the sphincter between the stomach and small intestine is to
(A) retain chyme in the stomach until pepsin digestion is complete.
(B) periodically release chyme into the small intestine in squirts.
(C) release bile into the duodenum when chyme is present.
(D) release pancreatic secretions into the duodenum when chyme is present.
(E) pancreatic secretions transiently into the duodenum when chyme is present.

16. Plasmodium, the organism that causes malaria, is a(n) (A) amoeba. (B) stramenopile. (C) ciliate. (D) alveolate. (E) excavate.

17. Which option correctly represents the most likely sequence of the evolution of plants, from earliest to most recent? (A) bryophytes, seedless vascular plants, gymnosperms, angiosperms (B) seedless vascular plants, bryophytes, angiosperms, gymnosperms (C) bryophytes, seedless vascular plants, angiosperms, gymnosperms (D) bryophytes, gymnosperms, seedless vascular plants, angiosperms (E) bryophytes, angiosperms, seedless vascular plants, gymnosperms

18. Which structure is found in angiosperms but not gymnosperms? (A) root (B) spores (C) seeds (D) ovule (E) fruit

19. Most familiar types of fungi including mushrooms, puffballs, and shelf fungi are examples of (A) chytrids. (B) ascomycetes. (C) zygomycetes. (D) basidiomycetes. (E) streptomyces.

21. Which hormone is produced by adipose cells and helps to control appetite? (A) insulin (B) bile (C) gastrin (D) leptin (E) interferon

22. Which statement regarding breathing and circulation in insects is false? (A) Insects lose very little water by using a tracheal system to breathe. (B) The tracheal system of insects consists of a series of branching air tubes that extend from the surface to deep inside the body. (C) Terrestrial animals such as insects spend much more energy than aquatic animals to ventilate their respiratory surfaces. (D) The circulatory system of insects is not involved in transporting gases. (E) Insects spend little water by using a tracheal system to breathe.

23. What part of the human brain contains control centers that establish a breathing rhythm? (A) midbrain (B) cerebellum (C) pituitary (D) thalamus (E) medulla oblongata

複選題24. Which statement about mammalian circulatory systems is false? (A) The pulmonary circuit carries blood between the heart and the lungs. (B) The systemic circuit carries blood between the heart and the rest of the body. (C) Mammals have two atria and two ventricles in their hearts. (D) The left side of a mammal's heart sends blood to the lungs. (E) The pulmonary circuit carries blood between the heart and the body.

25. In mammals, blood returning from the head will pass through the ________ just before entering the right atrium. (A) left atrium (B) superior vena cava (C) inferior vena cava (D) aorta (E) right atrium

26. During ventricular systole, the semilunar valves ________ and the AV valves ________. (A) open； open (B) close； open (C) open； close (D) close； close (E) open, unchanged.