The piston cooling system may employ similar components, except that （） is used instead of a head tank. ["a sump tank","a feed well","a double bottom tank","a drain tank"]
室内分布系统一般来说，在离信号源较近处，用（）。在离信号源有一定距离或信号较弱时在无源分布基础上增加（）。在离信号源较远或施工难度较大时，采用有源分布方式或（）。对于长条形走廊、隧道、电梯等，采用（）。
The pistons are cooled by oil supplied from the forced （） system. ["fresh water","sea water","lubrication","fuel oil"]
设计直放站时，要求选择该处接收到的最强的、最稳定的施主小区信号，且尽量大于（）。
The period when both inlet valves and exhaust valves are open is referred to as （）. ["valve loop","valve uniflow","valve overlap","valve grinding"]
为了使高层建筑物的高层和底层有好的通话质量，应采用（）。它可以增加30％的话务量，而天线发射功率只有（）mw左右，对人体的辐射可以不考虑。
