是盾构施工的主要装配构件，是隧道的最内层屏障，承担着抵抗土层压力、地下水压力以及一些特殊荷载的作用。

A. The doctors acquire the pathogens from their patients when he examine the patient.
B. The pathogens invade the wound of a worker when he participated inconstruction of a new hospital.
C. The patient's infection was caused by not sterilized surgical scalpels .
D. The newly born baby get infection during delivery.

A. It is inactivated by 56℃within 30min,
B. Toxoid can be made from endotoxin,
C. They are LPS produced by G- bacteria,
D. They are best antigens.

A. They are less toxicthan exotoxins
B. They are more stable on heating than exotoxins
C. They bind to specific cell receptors，whereas exotoxins do not
D. They are part of the bacterial cell wall，whereas exotoxins are not.