Only when you experience the bad earthquake taking place in Si Chuan______ the importance of life.

A．can you understand

B．are you understand

C．do you understand

D．did you understand

"气行则血行，气滞则血滞"的理论依据是

A．气为血帅

B．血为气母

C．津能载气

D．津血同源

E．气能生血