The teacher, along with his students, _____ on the ground in the setting sun. [ ]

A. play

B. playing

C. is playing

D. are playing

颌骨巨细胞肉芽肿与颌骨巨细胞瘤易混淆，其主要鉴别诊断的依据是：（）

A．X线表现骨皮质变薄，膨胀

B．巨细胞大小及数量多少，巨细胞分布是否均匀

C．间质细胞有否异形和核分裂相

D．是否有出血

E．胶原纤维少