Never______ such a difficult problem. It took me almost half an hour to work it out.

A．had I come across

B．I had come across

C．did I come across

D．I did come across

患者男，17岁，左膝关节下方疼痛，肿胀，关节活动障碍2个月。查体：左膝关节下方肢体较对侧增粗3cm，表面皮温高，可见静脉怒张及局部压痛。X线片示左胫骨干骺端溶骨及成骨性破坏，可见日光放射样骨膜反应及软组织肿块。碱性磷酸酶485U/L。

以下中最可能的诊断是（）

A.骨髓炎

B.骨巨细胞瘤

C.尤文肉瘤

D.软骨肉瘤

E.骨肉瘤