还有一些待解决的问题。
其实没有这么复杂的,这里的不定式是remain这个单词的词法,查柯林斯词典:
1,If someone or something remains in a particular state or condition, they stay in that state or condition and do not change.
2,If you remain in a place, you stay there and do not move away.
3,If something remains to be done, it has not yet been done and still needs to be done.
...
不是所有的动词都可以接不定式结构的