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?
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.