下列属于生物的是( )
A:长蘑菇的朽木
B:咸鸭蛋
C:玉米
D:电脑病毒
I often ask my music teacher____ play the piano well.
过一点能画____条直线,过两点能画____条直线.
胎儿通过脐带与胎盘相连,胎盘的主要作用是( )
The firefighters soon got the fire in the building________.