You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to choose a gastroenterologist [title] Get a referral. [step] Ask your primary care doctor if they can recommend a gastroenterologist. See if your friends, family, or other members of your social circle can offer you a referral. <sep> (A) If you feel particularly up to it and you know people at work who are potentially candidates, you may even ask them to join you for a trial consult. [substeps] Your physician may have recommendations you've had many professional appointments with. (B) Alternately, if you already used a pediatric gastroenterologist in the past, then you might want to ask your primary care doctor for one. [substeps] It isn't necessary to ask friends, family, or colleagues for referrals, but it is a good idea to ask often. (C) [substeps] Make sure any referrals are trustworthy. People who are still in medical school can't be contacted because they were unable to leave early. (D) [substeps] If you know anyone who required the same procedure or has the same illness as you, ask them if they would recommend their gastroenterologist. Try to get more than one referral so you have options.
Output:
D