They are only study(还是studying) for long time.

问题描述:

They are only study(还是studying) for long time.

studying

be only doing
固定搭配

studying
虽然study可以用作名词 表示学习 不过用在这里不通啊 你不能说他们是学习

当然是studying
be doing 固定句式

studying
有are了,当然是studying

studying
这是现在进行时态,由主语+be+动词-ing(现在分词)构成