To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to （）. ["re-adjust the discharge pressure","clean the expansion valve screen","add refrigerant","adjust the expansion valve"]
电焊引起的火灾原因是什么？怎样预防？
对于Excel工作表中的文字型数据，（）。 ["不可以排序","只可按“拼音”排序","只可按“笔划”排序","既可按“拼音”，又可按“笔划”排序"]
On small, low pressure, air compressors, the cylinders are usually lubricated by the （）. ["splash method","mechanical force feed lubricators","detached sump method","internal cooling passages in the crankshafts and connecting rod"]
白炽灯的火灾的原因是什么？怎样预防？
行灯、电钻等移动式电气设备的火灾原因是什么？怎样预防？
