Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to make a hamster playpen [title] Build the walls of the playpen with something slippery. [step] A playpen needs to be a safe place for your hamster to explore, so it shouldn't be made of materials a hamster can climb or chew. Corrugated plastic is a great option as it is not only slippery, it can easily be cut to any size you need.

Ending1: Another great option is a large rubbermaid-type container with tall sides. [substeps] You can attach pieces of plastic together with anything from binder clips to duct tape. Ending2: [title] Attach a tube the size and shape of your pet's snout. [step] Leave enough room for your animal to explore, but not so much that you can cover it entirely. Ending3: [title] Use construction paper to cut a large rectangle around the perimeter of the playpen. [step] Use a pencil, or a marker to mark both the top and bottom sides. Ending4: Wood mulch does the same for cardboard. It also helps for insects such as cockroaches and mice.

Answer format: ending1/ending2/ending3/ending4