1st Class or 2nd Class Control

angle Class Ⅱand skeletal class I malocclusion

Class Ⅰ and Class Ⅱ highways

Class A and class B infectious diseases

Class I and Class II

5-step ship lock

accelerator lock

access control lock

access lock

active-lock

actively mode lock

adapter lock

adding current lock

adjusting bracket lock bolt

adjusting nut lock

adjusting ring lock

aid to navigation in lock area

air lock

air lock valve

Air-Lock