Answer:
D. He greatly improved communication.
Step-by-step explanation:
The word "revolutionized" is used to refer to the act of bringing about a huge change in something. We can also say that the term means that there is a transformation, a complete change from what it was previously.
In the given sentence, it is used to refer to Marconi's act of bringing about a change in the way messages are transmitted. This means that he brought a huge change, a transformation to how people communicate.
Thus, the correct answer is option D.