Which invention is correctly associated with the early American inventor David Bushnell?

Introduction / Context:
This question tests knowledge of inventions from early military technology, focusing on a device associated with David Bushnell, an American inventor during the eighteenth century. He is remembered for designing one of the first military submarines, called the Turtle, which was used experimentally in the American Revolutionary War. The question asks which invention among the options should be correctly linked with his name, an important detail in the history of naval technology.

Given Data / Assumptions:

• The inventor in mind is David Bushnell, an early American innovator.
• The options list atomic bomb, submarine, theory of isotopes (Urey) and hovercraft.
• The task is to select the invention that Bushnell is known for.
• Standard general knowledge about naval and military inventions is assumed.

Concept / Approach:
Bushnell designed the Turtle, a hand powered submersible boat intended to attach explosives to enemy ships in harbour. While its missions had limited success, it is widely recognised as one of the first practical attempts at a submarine used in warfare. The atomic bomb was developed much later during the twentieth century by scientists working on the Manhattan Project. The theory of isotopes is associated with Harold Urey and other modern chemists, not Bushnell. The hovercraft is linked to Christopher Cockerell. Therefore, the correct association for Bushnell is with the submarine.

Step-by-Step Solution:
Step 1: Recall that David Bushnell lived during the era of the American Revolution and worked on devices to attack British ships. Step 2: Identify that his most famous invention was the Turtle, an early one person submersible vessel. Step 3: Recognise that the Turtle is often described as one of the first submarines used in combat, even though it was primitive by modern standards. Step 4: Compare this recollection with the options given in the question. Step 5: See that option B, submarine, directly corresponds to the nature of Bushnell's invention. Step 6: Therefore, choose submarine as the correct answer.

Verification / Alternative check:
A quick verification is to recall that the atomic bomb belongs to the twentieth century period of nuclear physics and the Second World War, far removed from Bushnell's lifetime. The hovercraft is a twentieth century craft developed by Christopher Cockerell. The mention of Urey reminds us of Harold Urey, a chemist known for isotopes and the discovery of deuterium. None of these later scientific developments align with an eighteenth century inventor involved in the American Revolution, confirming that the submarine is the correct match.

Why Other Options Are Wrong:
The atomic bomb required advances in nuclear physics, radioactivity and engineering that took place long after Bushnell's time, so it cannot be his invention. The theory of isotopes and related discoveries such as deuterium are associated with Harold Urey and other twentieth century scientists, not with an eighteenth century military inventor. The hovercraft, which glides on a cushion of air over land or water, is primarily linked with Christopher Cockerell's mid twentieth century work. Therefore, these options do not correctly describe Bushnell's contribution.

Common Pitfalls:
Examinees may be misled by unfamiliar historical names and guess among late twentieth century inventions, forgetting to consider the time period implied by the context. Another mistake is to mix up inventors associated with water related technology, treating every marine innovation as interchangeable. To avoid these errors, it is helpful to connect Bushnell with the Turtle submarine and to remember that early submarines were already being attempted long before nuclear weapons or hovercraft were conceived.

Final Answer:
The invention correctly associated with David Bushnell is the early military Submarine known as the Turtle.