The little child usually felt frightened at night, so not until ___________.

A．did he fall asleep his mother left the room

B．he fell asleep had his mother left the room

C．did he fall asleep did his mother leave the room

D．he fell asleep did his mother leave the room

视网膜母细胞瘤的常见染色体异常表现为（）

A.14q-13

B.13p-14

C.13q-14

D.14q-14

E.13q-14和14q-13