PaO₂低于25mmHg一段时间后，脑血流的自动调节会丧失，这段时间是（）。

A.2～3min

B.3～4min

C.4～6min

D.6～8min

E.8min以上

翻译下列短语

1. lead to ____  

2. object to ____

3. refer to ____    

4. stick to ____

5. add to _____  

6. add up to____

7. compare... to ____                    

8. see to ____

9. get close to____

10. get down to ____

11. get/be used to____

12.  pay attention to____

13. put an end to ____

14. admit to___

15. devote ... to ____