Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to whelp large breed dogs [title] Prepare the whelping box. [step] The whelping box is the space in which your dog gives birth to its puppies. It is also the space to which all puppies should return after their mother has completed birthing its litter.

Ending1: You can buy a whelping box commercially or construct one from wood or a cardboard box. [substeps] If you think your dog will become pregnant again, you might as well invest in a sturdier commercially-made whelping box. Ending2: Make sure the whelping box is clear of anything dangerous or harmful to your dog. [substeps] You may also empty the box of small objects and clutter into it. Ending3: Some breeders ask to confine the first line of puppies and leave them in wait while the mother performs deliveries. Some breeder officials recommend that the semen materials be kept a single inch (0.64 cm) from the wall. Ending4: [substeps] Make sure that the box is big enough for both dogs to get in and out comfortably and without wobbling. There should be plenty of nooks and crannies to allow your dog the privacy and comfort that it needs in the box.

Answer format: ending1/ending2/ending3/ending4