The model for Leonardo da Vinci's Mona Lisa is believed ____ in the convent (修道院) at the age of 63 in 1542. [ ]

A. to die

B. to have died

C. dying

D. having died

患者，男，35岁。因服吲哚美辛数片后觉胃痛，今晨呕咖啡样胃内容物400ml来诊。既往无胃病史。首选的检查是

A．血清胃泌素测定

B．B型超声检查

C．X线胃肠钡餐

D．急诊胃镜检查

E．胃液分析