47 What is the detail given to explain the deafness caused by accident?
(A) chickenpox
(B) influenza
(C) a blow to the ear
(D) inbreeding

   In the United States, there are about twenty-two million hearing-impaired損害、（身體功能）障礙 people; of these, two million are profoundly深刻、極度 deaf (unable to hear any thing) or severely deaf (unable to hear much).

Hearing impairment results from three major factors that are not necessarily exclusive專有、獨佔的、昂貴: environmental, hereditary遺傳、世襲 and old age. 

   Environmental causes include noise-induced誘使、勸說、導致、催生, accidental, toxic, and viral病毒. Noise-induced deafness is primarily主要地 a phenomenon of the modern industrial world, though stonemasons石匠, may have been subject to hearing-loss in the ancient world. permanent長久、永久 deafness resulting from toxicity is also a phenomenon of the modern world. Deafness from accident, such as a blow to the ear, must have resulted from time to time. Viruses, too, were very much part of the ancient world. Of the six main viruses that can cause deafness today—chickenpox水痘, common cold viruses, influenza流行性感冒, measles麻疹, mumps流行性腮腺炎 and poliomyelitis脊髓灰質炎 there is evidence for five in ancient Greece. There is also evidence for the presence出席、在場、存在、儀態，風度；氣質 of bacterial細菌 meningitis腦脊膜炎, whose classic complication併發症 is hearing loss. In modern, developed countries, preventative medicine reduces the incidence事件、發生率 and severity嚴重、不和善 of these viruses, but in the ancient world, as in third-world countries today, these viruses must have taken their toll損失、傷亡、收費、鐘聲、喪鐘. 

   There is no reason to rule out hereditary deafness in the ancient world, and there is some conjectural推測 evidence for the results of in-breeding繁殖，飼養, although not specifically for deafness. In addition to inbreeding, other hereditary factors would have produced deafness. Some families simply have a genetic background that favors deafness.