just can't, can't just

[joham]

The biggest problem for most plants, which _____ just get up and run away when threatened, is that animals like to eat them.
This was one of China's university admission examination questions. The given answer is: "can't". I thought "can't just" meant "can't only" and so was not suitable for the sentence. I also thought the sentence should have been "..., which just can't get up and run away...". Am I right?

Thank you very much.

 

[schmoozed]

consider what's between the commas as a piece of info, skip that and read the sentence and it makes sense. Now to that info...the point is plants aren't animals...why...bcos they can't get up seeing a predator and run away - much like the way animals behave. This is said in a colloquial way. So the Chinese answer seems to be gramatically valid.

But your alternative (just can't) is even better.

Good find pal.

 

[Anglika]

There is a difference between "just can't do something" and "can't just do something".

The plants just can't get up... The plants cannot manage to get up
The plants can't just get up... The plants cannot merely/simply get up

The answer is correct.