Write the next sentence in the following story.

How to care for corydoras
Get a good-sized tank.
Corydoras are not very large fish, and generally don't need too much room. A 20-gallon tank should be plenty big enough for a small school of non-dwarf corydoras (6 fish).

Pick your answer from:
a). To ensure the corydoras get enough oxygen and energy, buy a large tank of three or four. You'll want enough room for 2-6 young corydoras for every 8 adult adult sized corydoras you have..
b). To find a good sized tank, consult your local pet store to find the right size of tank for your corydoras. Size your tank to suit the amount of corydoras..
c). Of course, if you consider adding more fish, whether corydoras or something else, you'll need a bigger tank. There is a traditional " rule of thumb " that suggests 1-gallon per inch of fish that you put in the tank..
d). Large corydoras can sometimes get cramped and old. A 10 " tank will be your best bet... The answer should be
c).