When you feel helpless and _______, just remember you are not _____ in the world

because your friends are around you, including me.

A．alone; alone

B．lonely; lonely

C．lonely; alone

D．alone; lonely

是起始于釉牙本质界伸向釉质的纺锤状结构，是成牙本质细胞胞浆突的末端膨大并穿过釉牙本质界包埋在釉质中所形成的( )

A．釉丛
B．釉梭
C．釉板
D．釉牙本质界
E．釉质的生长线