___ with various research projects, that scientist can’t even find time to visit his parents.

A．Occupying

B．Occupied

C．To be occupied

D．To occupy

1.5岁男婴，口内检查发现，上下颌乳中切牙和乳侧切牙均已萌出，按照一般乳牙萌出顺序：在其口内萌出的下一颗牙为

A．上颌第一乳磨牙

B．上颌乳尖牙

C．下颌乳尖牙

D．下颌第一乳磨牙

E．下颌第二乳磨牙