Young as he is, David has gained ____ rich experience in ____ society.

A．the; the

B．a; 不填

C．不填；不填

D．不填；the

食管癌病人出现持续胸痛或背痛多表示()

A．癌肿部位有炎症

B．癌肿已侵犯食管外组织

C．癌肿侵犯交感神经节

D．有食管气管瘘

E．癌肿较大