Inside a rat's nose are up to 1,000 different types of olfactory receptors whereas humans only have 100 to 200 types.
2017年12月四級真題（第一套）閱讀 Section A
Rats are often?associated with spreading disease rather than?preventing it, but this long-tailed animal is highly?sensitive Inside a rat's nose are up to 1, 000 different types of olfactory receptors whereas humans only have 100 to 200 types.