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 students( who are) playing basketball.
相信你能理解赞同吧