宣传工作“三贴近”是指（）。

A．Directly connected to the side tube of tracheal canula
B．Gradually approach the side tube of tracheal canula until the respiratory curve changes significantly
C．Stay away from the side tube of the tracheal canula by more than 5cm to avoid inhaling too much CO2
D．Insert directly into the rabbit's nasal cavity
E．Connect directly to the breathing transducer