As for the multiple-choice questions on automatic devices in power systems, please ask experts to do it. The teacher will explain it in a few days and just give you the answer. Thank you.
3. (B)
4. (B)
17. (D)
25. (D)
27, (B)
29, (C)
31, (A)
32, (B)
33. (A)
37. (D)
46. (ABC)
48. (BCD)
49. (ACD)
50. (ABD)
The other ones are not 100% sure.