单项选择题
在电磁波的接收端，为了接收到所有需要的电磁波，并将信号取出，需要经过
A、需要用能量转换补件补捉波，然后再调谐和检波
B、需要用能量转换补件补捉波，然后进行调制和调谐
C、调解和调幅
D、调频和解调
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问答题Read the following passage and decide the underlined part of the statements are facts (F) or opinions (O). Fill in the blanks with F for facts, O for opinion. (答案请输入大写字母，答案与答案之间无空格。）
The Box Boy
I was 16 when I found the first job. It was packing groceries. I thought everything was fine, until the end of the first day, when the manager told me not to return. I wasn’t sacking fast enough. I was a painfully shy kid, and I surprised even myself when I blurted out, “Let me come back tomorrow and try one more time. I know I’ll do better.” Speaking up went against my very nature, but it worked. I got a second chance. If you want to accomplish anything in life, you can’t just sit back and hope it will happen. You’ve got to make it happen. I was not a natural athlete when I began studying karate, but I trained harder than anyone else and was a world middleweight karate champion for six years. Later, when I decided to become an actor, I was 36 and had no experience. There were maybe 16,000 unemployed actors in Hollywood, and I’d be competing against guys who had already been in movies or on TV. If I had said, “I don’t stand a chance,” one thing is clear: I wouldn’t have. People whine, “I haven’t succeeded because I haven’t had the breaks.” You create your own breaks.
Chuck Norris( Famous actor who has starred in over 20 feature films)
3. ( ) I thought everything was fine, until the end of the first day, when the manager told me not to return.
4. ( ) I trained harder than anyone else and was a world middleweight karate champion for six years.
在区间
上的最小值是
.