1. Most metals are extracted from ___.
a) ore b) ear c) air
2. Ore always contains ___.
a) all the chemical elements b) some impurities c) only pure metal
3. To get the pure metal metallurgists use special ___.
a) furniture b) furnaces c) solvents
Text 4. How Did the Computer Mouse Come into Being?
The development of the computer mouse as an essential input device followed on the heels of numerous changes to the operating environment of personal computers. Initially, there was no need for a mouse, because there was nothing to point to on a computer screen. Early computers had primitive interfaces that used crude methods to receive data, like punch cards or teletype machines. Once graphical user interfaces were created, however, and pointing became an essential part of interacting with a computer, the mouse soon became the input device of choice in personal computing. The first mouse to have commercial success debuted with Apple’s Macintosh computer in 1984.