If this is on personal opinion, I would say the initial creation of the telephone. Even though a smartphone practically kickstarted a whole era to technology that is still going on till this day, it was the telephone that started this all. If it wasn’t for the idea to create a phone that is more advanced than a box attached to the wall, none of these advancements would’ve happened at all. (Although that is uncertain, things do tend to have a way of working out in the end. If someone didn’t invent it, another person would’ve thought of it sooner or later.) But that is only if we’re talking long term, which I prefer because there was no limit to when the results of impact started in the prompt stated above, yet if we were to speak short term and the faster one, the credit would go to the smart cellphone. But we aren’t, because the question never specified ;)
Option (a) is true that the computers have become smaller and smaller with advancement of the technology. The earlier version of computers used vacuum tubes and are very big in size.
As the years passed and due to the advancement of the transistors the computers have become smaller in size.
Option (b) is true. With the advancement in the research in circuits used in the computer like Integrated Circuits the computers have become faster.
The response time of the operating system has reduced drastically.
Option (c) is wrong option. The computers have become cheaper. The transistors are cheaper compared to the vacuum tubes which are used in the earlier computers.
The price of the same computer (memory and time efficiency) has become less in the coming years than in the previous years with the advancement in the research of transistors.
Option (d) is true. Now-a-days computers support more and more number of applications. Computers has more number of applications in various and diversified fields.
With the advancements in the computers, the computers are finding more applications in different fields like medicine, law, transport industries etc.
