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.