Here are the best answers to each question based on the context provided:

36. Phong: My uncle called this morning. A flood destroyed his house.
Mark: **B. I’m sorry to hear that.**

37. What were you doing when the volcano ______?
**C. erupts** (correct past tense: "was erupting")

38. I ______ TV at 9 p.m. yesterday.
**C. wasn’t watching**

39. Water pollution can put negative ______ on our health.
**C. effects**

40. Rescue ______ are trying hard to save people in the flooded area.
**B. workers**

41. You should turn on **(B) devices** while you are not using them.
**(B) devices** (should be "the devices")

42. An **(A) open-air market** often offers a wide range of **(C) products**.
**(C) products** (correct as is)

43. You can stay **(A) with us before** you find a suitable place to **(D) stay.**
**(C) find** (should be "find")

44. Listen to the **(A) announcement**, the train won’t leave until 12:00. Let’s get something to drink **(D).**
**(A) announcement** (correct as is)

45. Look at the advertisement. Will the big sale **(B) start** next Friday?
**(B) start** (correct as is)

Let me know if you need any further assistance!