Sure, here are the correct answers for each question:

25. **C. When** was Doimoi officially initiated? - In 1986.

26. **A.** The correct sentence should be: "Susan stopped writing her letter because she had to leave for the hospital." The error is in "to write"; it should be "writing."

27. **B.** The correct sentence should be: "We didn’t have much knowledge about physics." The error is in "many knowledge"; it should be "much knowledge."

28. **A.** The correct sentence should be: "We were advised not to drink the water in the bottle." The error is in "not drinking"; it should be "not to drink."

29. **C.** The correct sentence should be: "The storm prevented us from going out." The error is in "to go out"; it should be "from going out."

30. **C.** The correct sentence should be: "If you listen to the questions carefully, you will answer them easily." The error is in "would answer"; it should be "will answer."