21. Unless an extension at least one week before the due date, it will not be given.

　　a. you request c. you requested

　　b. you will request d. requesting

　　22. The assignment made me .

　　a. to think hard c. think hard

　　b. thinking hard d. thought hard

　　23. The scientists were prohibited the danger zone.

　　a. to enter c. enter

　　b. entering d. from entering

　　24. the right answer I would have got full marks.

　　a. Had I known c. If I’ll know

　　b. if I would have known d. If I was knowing

　　25. The results were convincing that we decided to publish them.

　　a. so c. very

　　b. such d. so much

　　26. way you do it, the answer is always the same.

　　a. However c. Who ever

　　b. whichever d. Why ever

　　27. producing methane, the process also produces carbon monoxide.

　　a. Apart c. Besides

　　b. As well d. In addition

　　28. The biologist admitted excessive numbers of animals in laboratory tests.

　　a. using c. being used

　　b. to use d. used

　　29. A whale is a mammal, it is warm-blooded and gives milk to its young.

　　a. who c. which means that

　　b. which d. that

　　30. He appears minor problems.

　　a. to have had c. was having

　　b. having d. had