C is not a bad answer but initially in any setting one should try to go from broad to narrow. We have a partial history we don't have info regarding a physical besides from the question stem that he "walked" into the ER and that he "tells"- this was to show you that he's currently stable which is one of the key things we would want to get from the physical exam. After getting subjective data we would want to move on to objective data ie= getting lab work/imaging/others....
Hence the answer here would most probably be get blood work G. Vitals was also thrown in there although usually you get them with the patient in the ED.
In the lab work we would look for Hct- to see if it's a chronic problem or new, Leukocytosis may help in a wide array of GI problems, PT/PTT can tell us if he has coag problem. LFTs' can hint for varices ETC....