A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers  ${140}^{0}F.$ What is the temperature as registered by the centigrade thermometer?

• A

  ${30}^{0}C$

• B

  ${40}^{0}C$

• C

  ${60}^{0}C$

• D

  ${80}^{0}C$