呵呵 楼主转牛角尖了,have some problems in theri study 的in theri study是一个短语!构成一个句子就是在他们学习中遇到一些问题!!其实还是要结合语境来看,介词这东西不一定固定!!
have some problems / a problem (in) doing sth
have difficulty (in) doing sth
have some problems in their study(这应该是错误的表达法,正确的是)------have some problems WITH their study (记住,书也是人编的,所以错误是难免的)
have some problems 和have difficulty用法基本相同,后面连接 with sth 、(in) doing sth、in sth,都可以。不仅仅是两种,你举的例子属于最后一种情况。