Please choose the correct ending to complete the given sentence: Work World: [header] How to train your service dog without a professional trainer [title] Find a dog that is the right age. [step] It can be difficult to know if a puppy under the age of 6 months has the right blend of intelligence and attention to make a good service dog. Charity's that train up service dogs, have a high' drop out' rate, even when they have used their knowledge to select likely candidates.

Ending1: After awhile, however, the breed or age they assume must be in one of their breeding levels. Large breed dogs are always at their leanest. Ending2: [substeps] Buying a puppy with the express purpose of it becoming a service dog is a gamble. It might be better to source a young dog which has been properly trained and has established their personality already. Ending3: [substeps] Stock more specialized training techniques such as a walk with your dog, fetch, and urine potty training style. [title] Consider training your dog to be upper class dogs. Ending4: This makes the best decision for your first professional approach. [substeps] You need to think carefully before buying a dog and if you would like to manage the dog better.

Answer format: ending1/ending2/ending3/ending4