Can a strand not be synthesised in 5' -> 3' direction?
It sounds like your guess was right and the exception is the lagging strand. The statement is phrased poorly, but it seems like they were going for the lagging strand. Either they meant for you to think that
-the lagging strand is growing 3' to 5'
or, more likely,
-the polymerase is only synthesizing on one (leading) strand at a time
While technically the book was correct, it was a trick question and phrased unfairly.
You are completely right that DNA is synthesized from 5' to 3'. I don't know of any exceptions to this, but hesitate to say anything overly definitive because there are so many rare exceptions in science. I can say with some confidence that DNA polymerase cannot ever synthesize in the 3' -&gt; 5' direction. If you haven't already, I highly recommend checking out the Khan Academy article, Molecular mechanism of DNA replication! Nature Education also has a pretty good article on the topic, Major Molecular Events of DNA Replication.