Wait for a few minutes, your watch____ now.

A．will be repaired

B．has been repaired

C．is being repaired

D．has repaired

低O2和H+浓度增加时呼吸增强的主要原因是

A．直接兴奋呼吸中枢

B．刺激外周化学感受器

C．刺激中枢化学感受器

D．兴奋肺牵张感受器

E．刺激呼吸肌