关于电磁现象，下列说法中正确的是(    )

抗战时期，***在国民党统治区公开发行的机关报是（    ）

记miin{a，b}表示a，b中较小的数，比如min{3，﹣1}=﹣1，设函数f（x）=|min{x²， ${\log }_{\frac{1}{16}}$ x}|（x＞0），若f（x₁）=f（x₂）=f（x₃）（x₁，x₂，x₃互不相等），则x₁•x₂•x₃的取值范围为____

    This story is about a young man. He worked very hard at his lessons, so he was too busy to have a rest. At last, he couldn't go to sleep every night. When he went to bed, he closed his eyes and tried to sleep.But the more he tried, the more he stayed awake.

    After a while, he decided to visit the doctor."I just can't go to sleep at night. What should I do?" "I have a suggestion,"said the doctor, "try counting numbers. By the time you reach one thousand, you'll be asleep. I'm sure of it. The next day the man returned to the doctor's office."well," said the doctor, "How are you today? Did you try my suggestion?"

    The man still looked tired, "Yes,"he said, " I tried counting one, two, three…up to one thousand. But when I reached five thousand and sixty-nine, I began to feel sleepy. I had to get up and drink some tea so that I could go on counting up to one thousand, but then I still couldn't fall asleep.

下列反映中外友好交往的史实有（    ）

①丝绸之路   ②遣唐使  ③郑和下西洋  ④册封“班禅额尔德尼”