The correct answer is D. invented.
James Watt invented the steam engine in 1769. He was a Scottish inventor and mechanical engineer who improved on Thomas Newcomen’s atmospheric engine with his Watt steam engine in 1776, which was fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.
A discovery is the finding of something new or previously unknown. A manufacture is the process of making something from raw materials. A creation is something that is made or produced. An invention is something that is created or invented.
In this case, James Watt invented the steam engine, which was a new and previously unknown machine. He did not discover it, manufacture it, or create it. He invented it.