中枢化学感受器最敏感的刺激是:
A. 血液中的CO2
B. 脑脊液中的CO2
C. 血液中的H+
D. 脑脊液中的H+
E. 动脉血O2分压降低
生理情况下,血液中调节呼吸的最重要因素是:
A. PCO2
B. PO2
C. [H+]
D. [OH-]
E. [HCO3-]
1. ____ will leave for Beijing.
A. Now there the man
B. The man here now
C. The man who is here now
D. The man is here now
2. The weather ____.
A. wet and cold
B. is wet and cold
C. not wet and cold
D. were wet and cold