Because metalloids are semiconductors. The fact that metalloids are brittle/shiny are only physical characteristics and wouldn’t be the reason why a metalloid would be helpful for designing a new computer processor. Amphoteric means that it’s able to react both as a base and as an acid, but since the computer processor has to have something to do with electricity, the second option would be the answer. Semiconductors are also helpful for electrical circuits, so that’s also why is would be best for the new computer processor.