_________ needs further discussion whether we'll build a laboratory or not.
34. This is____ a difficult problem ____ all of us can't work it out.
33. Only when ____in the afternoon _____able to leave.
32. ---- I usually take a walk at night. ---- ___ do that.
39. Is this the reason ____ at the meeting for his carelessness in his work?
37. These wild flowers are so special that I would do___________I can to save them .