As the variance is the standard deviation squared, it's not uncommon to see it written in the form of (std dev)^2. I've got no idea why they chose to present it this way for this particular question, though I'm sure the markers won't mind which way you write it.
As a tutor, I personally find it useful to present it as SD squared as then I can compare the size of the SD with the mean and see if it looks wacky or reasonable!
