they are unable to analyze the complex issues that arise.该句中最后一词的'arise'是什么用法?是不是非谓语动词作定语?为什么不是arising?请详解

that arise.是that引导的定语从句，关系代词that指代的前面issues

修饰issues的 浮现出的问题

arise的意思是发生,这句话完全没有任何问题,是定语从句
他们分析不出已经发生了的复杂的问题
如果不能理解的话,把这句定于从句拆成两句话：
They are unable to analyze the complex issues.
The complex issues arise.
顺便给你讲一下arise的用法吧：
1.VERB发生；出现If a situation or problem arises,it begins to exist or people start to become aware of it.
...if a problem arises later in the pregnancy...
如果在怀孕后期出现问题
The birds also attack crops when the opportunity arises.
一有机会鸟儿们也会破坏庄稼.
2.VERB（由…）产生,引起If something arises from a particular situation,or arises out of it,it is created or caused by the situation.
...an overwhelming sense of guilt arising from my actions...
我的行为带来的沉重的罪恶感
The charges arise out of a long-running fraud enquiry by Merseyside police.
这些指控是默西赛德郡警方对诈骗案进行长期调查后提出的.
3.VERB形成；产生；成立If something such as a new species,organization,or system arises,it begins to exist and develop.
Heavy Metal music really arose in the late 60s.
重金属音乐真正形成于60年代后期.
4.VERB起床When you arise,you get out of bed in the morning.
He arose at 6:30 a.m.as usual.
同往常一样,他在早上6：30起了床.
5.VERB起立；起身；站起When you arise from a sitting or kneeling position,you stand up.
When I arose from the chair,my father and Eleanor's father were in deep conversation...
当我从椅子上站起来时,我父亲和埃莉诺的父亲谈兴正浓.
Arise,Sir William.
起立,威廉爵士.