口腔不良习惯包括以下各项的有
A．唇习惯
B．咬物习惯
C．偏侧咀嚼习惯
D．吮指习惯
E．舌习惯
参考答案：A,B,C,D,E
已知两定点F1(-5,0)、F2(5,0),动点P满足|PF1|-|PF2|=2a,则当a=3或a=5时,P点的轨迹为( )
A．双曲线和一条直线
B．双曲线和一条射线
C．双曲线的一支和一条射线
D．双曲线的一支和一条直线
While in drydock your vessel will be belt-gauged.This process involves（）.
A.measuring the thickness of the tail shaft liner
B.taking the vessel's offsets to check for hull deformation
C.testing and examining the anchor cables for defective links
D.drilling or sonic-testing the hull to determine the plate thickness
