Mary practices ______ the piano every day. [ ]
A. to play
B. play
C. playing
D. plays
C
---Where is your brother? ---He is in Beijing. He _____ back in three days.
A.will come
B.comes
C.has come
D.came
根尖周肉芽肿内上皮不可能来源于()
A.Serres上皮剩余
B.Malassez上皮剩余
C.口腔黏膜上皮
D.呼吸道上皮
E.牙周袋壁上皮