The nurse is teaching a parent how to administer antibiotics at home to a child with acute otitis media. Which statement by the parent indicates that teaching has been successful（）

A. "I’ll give the antibiotics for the full 10-day course of treatment. "

B. "I’ll give the antibiotics until my child’s ear pain is gone. "

C. "Whenever my child is cranky or pulls on an ear, I’ll give a dose of antibiotics. "

D. "If the ear pain is gone, there’s no need to see the physician for another ear examination. "

人们为了防止鸟吃草籽，把一片草地用网子全罩起来，结果导致食草昆虫大量繁殖，草叶几乎被吃光，这是因为破坏了[     ]

A．物质循环

B．生存循环

C．生态系统

D．食物链