Outside air enters the lungs in humans because a) he air pressure increases in t

Question

Outside air enters the lungs in humans because a) he air pressure increases in the bronchioles. b) a sphincter at the beginning of the trachea opens. c) there is high air pressure in the alveoli. d) the diaphragm and the rib muscles contract. e) the vocal cords relax. Reproductive cycles of animals are controlled by a) hormones b) environmental factors c) seasonal temperature d) all of the above e) none of the above Which of the following environments is almost always required for external fertilization? a) A very dry habitat. b) A cold habitat. c) A hot habitat. d) A moist or aquatic habitat. e) None of the above.

Explanation / Answer

19 d diaphragm and rib muscles contract

20 a hormones control reproduction in animals.

21. D a moist or aquatic habitat

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.