In each of the questions below, a word is given, followed by four statements. From the options, choose the one that provides the combination of statements that can be joined using the given word.

With

1. The purpose of the air preheater is to recover the heat from the boiler flue gas.
2. This increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas. 
3. An air preheater (APH) is any device designed to heat air before another process (for example, combustion in a boiler).
4. The primary objective is of increasing the thermal efficiency of the process.