Computers have evolved from the early mainframe computers to the relatively small smart devices with high computing power used today. Which of the following inventions contributed to reduce the physical size of computers?

Integrated circuits shrank computer size by placing thousands of components on a single small chip.

Vacuum tubes were large, hot and fragile, making the earliest computers room-sized.

Transistors were smaller than tubes but still mounted individually on circuit boards.

The cathode ray tube is a display device, not a means of shrinking the computer.

Packing whole circuits onto silicon chips enabled today's compact smart devices.

The trend of ever more transistors per chip is captured by Moore's Law.