已知接成Y形的三个电阻都是20Ω,则等效△形的三个电阻阻值为( )。
A. 全是20Ω
B. 全是30Ω
C. 全是60Ω
D. 全是90Ω
2018年6月A级考试真题[音频]Part Ⅰ Listening Comprehension (20 minutes)Directions: This part is to test your listening ability. It consists of 4 sections.Section ADirections: This section is to test your ability to understand short dialogues. There are 5 recorded dialogues in it. After each dialogue, there is a recorded question. Both the dialogues and questions will be spoken only once. When you hear a question, you should decide on the correct answer from the 4 choices marked A), B), C) and D) given in your test paper. Then you should mark the corresponding letter on the Answer Sheet with a single line through the center.Example: You will hear:You will read: A) New York City.B) An evening party.C) An air trip.D) The man’s job.From the dialogue we learn that the man is to take a flight to New York. Therefore, C) An air trip is the correct answer. You should mark C) on the Answer Sheet with a single line through the center.[A][B][C][D]Now the test will begin.1. A) A training course. B) A work plan.C) Computer skills. D) Business management.2. A) He attended a summer school.B) He worked as a volunteer.C) He travelled around the country.D) He made a survey in a local hospital.3. A) He has been writing a paper.B) He has been studying all night.C) He has been playing games all night.D) He has been working on the night shift.4. A) Very clear.B) Too simple.C) Too long.D) Very good.5. A) He is having a meeting. B) He is in his office now.C) He is available next week. D) He is on sick leave.