最早萌出的乳牙是 ()
A.上颌乳中切牙
B.下颌乳中切牙
C.下颌第一乳磨牙
D.上颌第二乳磨牙
E.下颌第二乳磨牙
参考答案:B
—Jenny's husband got killed in the aircraft.
—That's why she was badly_________[ ]
A. cut out
B. cut up
C. cut down
D. cut off
以锈菌为例,简述其5种孢子形成的过程,其倍性与核型的变化情况。