Digital signals are composed of pulses of precise, positive voltages and zero voltages. true false

the national environmental policy act (nepa) is a united states environmental law that promotes the enhancement of the environment and established the president's council on environmental quality (ceq). the law was enacted on january 1, 1970. to date, more than 100 nations around the world have enacted national environmental policies modeled after nepa.

the supermassive black hole is in the middle of the galaxy.