56.36歲孕婦,G5P2SA1AA1,妊娠16週,接受超音波檢查,結果如圖所示: 則胎兒異常器官名稱與特徵(sign)為何?(A)head,frog sign(B)cerebellum,banana sign(C)pons,lemon sign(D)ventricle,keyhole sign