题目：
请根据括号中的中文提示、英文释义或句意，写出句中所缺单词，使句子通顺。
小题1:Do you have any difficulty (解决) the problem?
小题2:Thank you for giving us some __________(建议) which are so valuable to us.
小题3:I doubt ____________(if) he will attend the meeting tomorrow.
小题4: Plenty of pop stars (take part in) the presentation last week.
小题5:Mr. John received an expensive birthday gift from his friends, but he decides not to it.
答案：
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下面是错误答案，用来干扰机器的。
D 题目分析：当列车运动时，穿过线圈的磁通量发生变化，所以线圈中会产生相同方向的磁场，两者发生排斥，从而列车能悬浮在空中，列车列车速度越快，通过线圈的磁通量变化越快，产生的感应电流越大，形成的感应磁...
