单选题 It is estimated that, currently, about 50000 species become ______ every year.
  • A. extinct
  • B. instinct
  • C. distinct
  • D. intense
【正确答案】 A
【答案解析】本题考点为形容词语义辨析。extinct意为“灭绝”，其他选项意思不对。根据题意，A为正确答案。