it's ...that...为强调句型，it's 后加被强调部分，(被强调部分是句子中除谓语的其他任何成分 )意为：就是/正是.....there be...that...（that 引导从句）（从句经常可以和分词词组转换）There are some problems that remain to be solved.从句=remaining to be solved你的追问问题，分词词组分为现在分词词组和过去分词词组，由于remain是系动词，本身没被动，因而被动转移到不定式上。你可以记住这一点。在there be ...that...的定语从句中，如是主动，就能转换成现在分词词组，再如：There are ten student...
