This problem is said _____ three times.
41. This is a ______ problem, which can be seen from her ______ look.
40. It is obvious that lung diseases are____smoking.
39. As we have known from the map of the world, this is ______.
38. Nowhere else in the world______ cheaper tailoring than in Hong Kong.
37. I tried all I could do ______ the topic at the meeting, but failed.