Which of the following points correctly pairs boiler mountings with primary functions of boilers?

(i) Manhole - Melts and releases steam if the water level in the boiler drops too down,

(ii) Feed check valve - Prevents backflow of water into the feed pump,

(iii) Pressure gauge - Releases excess steam from the boiler to prevent overpressure,

(iv) Fusible plug - Allows the boiler to be drained for inspection and maintenance