支撑剂的选择主要是指选择支撑剂的类型和粒径，选择的目的是为了达到一定的（） ["裂缝宽度","裂缝渗透率","裂缝导流能力","裂缝长度"]
在Excel中，默认情况下，如果输入日期或数值，则（）。 ["左对齐","右对齐","居中","两端对齐"]
The unloading system on an air compressor will （）. ["increase compressor discharge pressure on demand","increase compressor operating speed as necessary","allow the motor to turn the compressor opposed only by friction","reduce the compressor frictional load when starting"]
什么是系统安全？什么是安全系统工程？
支撑剂按其力学性质可分为（）和（）两大类。 ["脆性支撑剂；韧性支撑剂","硬性支撑剂；软性支撑剂","固体支撑剂；液体支撑剂","国内支撑剂；国外支撑剂"]
称呼指的是什么？
