Tap I fills a tank completely in 4 hours while taps II and III can empty out the tank completely in 8 hours and 12 hours respectively. Then,

A. Tap I fills one fourth part of a tank in one hour.

B. Taps II and III, together can empty the tank completely in 20 hours. (Tap I is closed )

C. With all the taps opened together, the tank completely fills in 24 hours.

Choose the correct answer from the options given below :

A and C only