The correct answer is B) liquid refrigerant flooding back from the cooling coil. If the refrigeration compressor has a slightly high suction pressure accompanied by an abnormally low suction temperature, it indicates that there is an issue with the refrigerant flow, specifically liquid refrigerant flooding back from the cooling coil. This can happen when the cooling load is too high or the refrigerant flow is restricted, leading to an excess of liquid refrigerant in the suction line, which can be drawn into the compressor and cause the observed symptoms. The other options are incorrect because: A) a clogged sub cooler would likely result in high suction pressure and high suction temperature, not low; C) a minor accumulation of air or non-condensable gases would cause high suction pressure and high suction temperature; and D) a leaking king valve would not directly cause the observed symptoms.