For a gas turbine the pressure ratio may be in the range: A 2 to 3 B 3 to 5 C 16 to 18 D 18 to 22

For a gas turbine the pressure ratio is16 to18

A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between.

The basic operation of the gas turbine is similar to that of the steam power plant except that air is used instead of water. Fresh atmospheric air flows through a compressor that brings it to higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow. This high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft. The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas turbine determines the design so that the most desirable energy form is maximized. Gas turbines are used to power aircraft, trains, ships, electrical generators, or even tanks.

The highest temperature in the cycle occurs at the end of the combustion process, and it is limited by the maximum temperature that the turbine blades can withstand. This also limits the pressure ratios that can be used in the cycle. For a fixed turbine inlet temperature, the net work output per cycle increases with the pressure ratio (thus the thermal efficiency) and the net work output. With less work output per cycle, a larger mass flow rate (thus a larger system) is needed to maintain the same power output, which may not be economical. In most common designs, the pressure ratio of a gas turbine ranges from about11 to16.

Early jet engines had limited pressure ratios due to construction inaccuracies of the compressors and various material limits. For instance, the Junkers Jumo004 from World War II had an overall pressure ratio3.14:1. The immediate post-war SNECMA Atar improved this marginally to5.2:1. Improvements in materials, compressor blades, and especially the introduction of multi-spool engines with several different rotational speeds, led to the much higher pressure ratios common today. Modern civilian engines generally operate between30 and40:1. The three-spool Rolls-Royce Trent900 used on the Airbus A380, for instance, has a pressure ratio of about39:1.

16-18 It's

C16 to18  

the ratio will be16-18

My answer is C ... since en.wikipedia.org/wiki/Brayton_cycle ...states

The engine used a separate piston compressor and expander, with .... In most common designs, the pressure ratio of a gas turbine ranges from about11 to16.

I do not know. But I believe the answer maybe choice "C"