Which invention revolutionized electronic communication in the 20th century?

The radio and telephone were pivotal inventions that transformed electronic communication in the 20th century. The telephone allowed for real-time voice communication over long distances, fundamentally changing how people interacted and conducted business. It eliminated the constraints of distance and made communication instantaneous.

Similarly, the invention of the radio introduced a new medium for broadcasting news, entertainment, and information to large audiences. It enabled people to receive updates and connect with events happening around the world without needing to be physically present.

While the other choices present significant technological advancements, they either did not have the same immediate impact on communication (like the space telescope and television) or came later in the century (the computer and internet). The radio and telephone together laid the foundation for modern communication systems, making them crucial for the advancements that followed in both telecommunications and media.