Most personal computers have a firewall and virus protection. Why are these security programs needed?
A. They keep people from storing personal information on the
computer.
B. They keep harmful programs from entering the computer from the
Internet.
C. They keep analog signals from entering the computer from the
Internet.
D. They make sure digital information is sent out as a digital signal.

Dao makes a table to identify the variables used in the equations for centripetal acceleration. what quantities belong in cells x and y?

Simon is writing a story about an astronaut whose spacecraft has been boarded by space pirates. the astronaut has her lucky penny in her hand behind her back as the space pirates break into the control room. she has just locked the controls so that the ship is accelerating in the direction of the control room’s ceiling. simon wants the astronaut to use the penny to hit a button on the control panel to turn off the lights and escape. the button is located a short distance behind and below the astronaut’s hands. how should simon use the theory of relativity to describe what the astronaut must do in order to hit the button?

Atemperature inversion can cause a warm air mass to move over a colder air mass. this traps the colder air mass and prevents surface air from rising. this may result in which of these? a) smog b) acid rain c) freezing rain d) a thunderstorm