Which of the following is NOT a common type of ship propulsion system?

• A. Gas turbine
• B. Diesel engine
• C. Steam turbine
• D. Nuclear reactor

Answer: (D)

The main idea is that some propulsion methods are widely used across many ships, while others are limited to a small, specialized group. Diesel engines, gas turbines, and steam turbines cover the broad spectrum of commercial and military vessels: diesel engines are efficient and fuel-hamiliar for most ships, gas turbines give high power and compactness for fast or modern warships, and steam turbines have long served large ships where high power is needed. Nuclear propulsion, on the other hand, is not widely used on the global ship fleet. It requires a nuclear reactor, heavy regulatory and safety oversight, specialized infrastructure, and substantial upfront and operating costs. These factors limit its use to a very small subset of vessels—primarily certain naval ships like submarines and aircraft carriers—so it isn’t a common propulsion type for ships in general.