Which of the following statements are correct?

I. Practically all common refrigerants have approximately the same COP and power requirement.

II. Ammonia mixes freely with lubricating oil and this helps lubrication of compressors.

III. Dielectric strength of refrigerants is an important property in hermetically sealed compressor units.

IV. Leakage of ammonia can be detected by halide torch method.

Choose the correct answer from the options given below.