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【判断题】
PWM利用功率半导体器件的高频开通和关断，把直流电压变成按一定宽度规律变化的电压脉冲序列，实现变频、变压并有效地控制和消除谐波。A.
正确
B.
错误
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举一反三
【单选题】听力原文：M: I have never heard such a fascinating lecture on solar energy. But you don't seem being impressed. Don't you like it, Rose? W: Well, I must admit that I dozed off most of the time during the l...
A.
Enjoyable.
B.
Too complicated.
C.
Interesting.
D.
Touching.
【简答题】表示逻辑函数功能的常用方法有____、____、____等。
【单选题】I have often thought 19 I did not take the first step and Dad did not 20 the operation, I would have never “heard” the love.
A.
survive
B.
live
C.
operate
D.
recover
【单选题】Directions: In this section, you will hear three short passages. At the end of each passage, you will hear three or four questions. Both the passage and the questions will be spoken only once. After y...
A.
They cannot see the firefighters because of the smoke.
B.
They do not realize the er they are in.
C.
They cannot hear the firefighters for the noise.
D.
They mistake the firefighters for monsters.
【单选题】I have often thought 19 I did not take the first step and Dad did not 20 the operation, I would have never “heard” the love.
A.
since
B.
as
C.
if
D.
because
【单选题】听力原文：W: I've been reading about a new healthful snack food (19) . It's made from fish. Have you heard anything about it? M: No, I haven't. But I don't like fish very much anyway. W: Not m worry. Altho...
A.
Food canning.
B.
Kinds of fish.
C.
A new snack food.
D.
A food flavoring.
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