18. 一位 60 歲男性病患因吐血至急診，胃鏡檢查發現為胃潰瘍出血，當潰瘍具有下列何種特徵時，不必給予內視鏡止血治療？(1) gastric ulcer with a clean base(2) gastric ulcer with a non-bleeding visible vessel(3) gastric ulcer with flat pigmented spots(4) gastric ulcer with adherent clots(5) gastric ulcer with a spurting visible vessel(A) (1)(B) (1)＋(2)＋(3)(C) (1)＋(3)(D) (1)＋(3)＋(4)(E) (3)＋(4)