上颌切牙有
A.唇舌面的外形高点在中1/3B.中切牙切缘与近中切角近似直角C.上颌侧切牙近中切角似锐角D.上颌侧切牙舌窝较浅E.较常发生变异
参考答案:B
While watching television, .
A.the doorbell rang
B.we heard the doorbell ring
C.there was someone knocking at the door
D.we heard the doorbell rung
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