Write the next sentence in the following story.

How to take care of a land hermit crab
Buy a 5-10 gallon (18. 9-37.9 l) fish tank.
Allow a lot of room for them to roam around in.
Put sand in the tank.

I. You should put enough sand so that a hermit crab could fully cover itself with it. Place decorations in the tank, like rocks and miniature logs..
II. There are two advantages to this housing. First, sand is generally of little use and it's hard for tank owners to move in and not care if the hermit crabs get stuck or tamper into any sand..
III. Hermit crabs may use it as a slurry for food, so be sure to fill it up just deep enough. A good substrate is one to six feet (1.6 to 1.8 m) deep..
IV. This is to make it soft for the crab and it must be weeded and repotted every now and again. The better the sand you use, the softer your crab will be... The answer should be
I.