some of the sudents have trouble (make)complete sentences.为什么
问题描述：
some of the sudents have trouble (make)complete sentences.为什么
the best way to improve your english is （study) with a group.为什么?
答
第一空填making,have trouble doing sth.是固定搭配,解释为做某事有困难.
第二空填to study,这里不定时作表语,此句为系表结构,is是系动词,to study with a group是表语.