Answer:
56 (?)
Step-by-step explanation:
According to most sources:
"Saturn has 83 moons. Sixty-three moons are confirmed and named"
Saturn has been known to have a variable amount of moons-- or to put it simply; Saturn is believed to have a ton of moons, both discovered and undisovered-- this also means that the number will grow with every new confirmation.
As of now, Saturn has 63 moons but given the options, 56 is both the closest and most reasonable.
Unfortunately, I do not know the lesson and what it taught so if you are still confused and have the option it might be helpful to re-read.