Answer: Option D.
Technician A.
Step-by-step explanation:
Oil residues on hoses, it's components or fittings indicate an area where refrigerant may be leaking.
An oil spot on the A/C hose is an indication of refrigerant leak in the system. Good oil levels are important for the system good performance. If the level of oil is to low, the compressor will not have lubrication and if it is too high, the heat exchange will affected which will lead to poor air conditioning performance. If a leak is formed on A/C hose, an oil spots that collect dirts will disappear. An refrigerant leak detector will help verify if there is no leak in the system.
So Technician A is correct.