Here are the corrections for each sentence with the underlined parts that need correction:

34. She doesn't know **(A)** what to speak **(B)** with those who failed **(C)** the test **(D)** due to their laziness.
- Correction: **(B)** should be "to speak" instead of "what to speak."

35. I used to have **(A)** a very good time **(B)** with my grandmother **(C)** when I am **(D)** a child.
- Correction: **(D)** should be "was" instead of "am."

36. Susan's parents are looking **(A)** forward to their **(B)** final result **(C)** of the interview **(D)** present.
- Correction: **(D)** "present" should likely be omitted or replaced with something else for clarity.

37. If he **(work)** lazily, he will fail the final exam.
- Correction: **(work)** should be "works."

38. You must follow these safety instructions if you **(not want)** to get in an accident.
- Correction: **(not want)** should be "do not want."

39. Mono can come and join us if he **(like)** our club.
- Correction: **(like)** should be "likes."

40. Laura **(can)** be good **(time management)** if **(take)** a training course/school.
- Correction: **(time management)** should be "in time management" and **(take)** should be "she takes."

41. If he **(hc)** want/save **(electricity bills)**, must **(turn)** all **(electrical equipment)** before going out.
- Correction: **(hc)** should be "he," and "must" should be "he must."

42. If Lan **(not/want)** to gain **(weight)**, she should **(eat)** much fast food.
- Correction: **(not/want)** should be "does not want."

Feel free to ask if you need further assistance!