26.____ the problem of method is solved, talking about the task is useless.
A. Until    B. Since    C. After    D. Unless
27. We have produced 15% more cotton this year____ we did last year.
A. as             B. than              C. like               D. white
28.It is late; ____, I'm too tired to go out.
A. besides   B. except   C. except for   D. except that
29. Everything around us is ____ solid ..liquid ____ gas.
A. not .. .but...      B. either.. .or...  C. neither.. .nor...    D. whether.. .or...
30. He will come ____ you ask him. 
A. whether      B. unless     C. if     D. while
31.____ he will come or not is still unknown.
A. If    B. Where     C. That     D. Whether
32.I don' t know ____ to stay at home or go out.
A. whether     B. if      C. how    D. where
33. He spoke loudly ____ the audience could hear him clearly.
A. so             B. that            C. so that             D. in order to
34. The book is not easy.____ it's rather difficult.
A. On the one hand         B. On the contrary 
C. On the other hand         D. On the other contrary
35. You must work hard,____ you will not learn English well.
A. if             B. whether          C. otherwise         D. unless
36. It rained heavily,____ the basketball match had to be put off.
A. so that           B. when
C. otherwise          D. therefore
37. We must do ____ the people want us to do..
A. whatever       B. however
C. wherever         D. whenever
38. You are certainly right,____ others may say.
A. what  B. whatever   C. that    D. as
39.____ makes mistakes must correct them. 
A. Who  B. What   C. Whoever  D. Whatever
40.I’ll discuss it with you ____ you like to come. 
A. when       B. where      C. whoever     D. whenever
41.____ you work, you must always serve the people heart and soul.
A. Wherever      B. Whenever         C. Where           D. When
42.___you understand this rule, you will have no further difficulty.
A. Once         B. At once           C. Only             D. Only then
43.___ difficult the task may be, we must fulfil it this month.
A. No matter how B. No matter what       C. No matter when   D. No matter where
44. We can surely overcome these difficulties _,___ we are closely united.
A. so far as         B. so long as        C. as soon as         D. as well as
45.___ I know he will stay here for half a year.
A. as soon as      B. as long as         C. so far as           D. as well as
46. Please write me ____ you arrive in New York.
A. as well as      B. so long as         C. as far as           D. as soon as
47. That is not ____ I want.
A. that      B. why       C. what       D. whose
48. ___ he did it remains a secret.
A. What       B. Whom       C. Which       D. How
49. It is quite clear ____ he won't see us.
A. what       B. that       C. why      D. how
50. Would you tell me ____ way I should take?
A. what      B. that     C. which    D. whose