A school principal trying to find out if parents will help buy new playground equipment shows digital leadership by asking the school board to ask parents. creating an e-mail survey for parents. ordering the equipment and asking parents to contribute. setting up a web conference for a small group of parents.

Which of these is a disadvantage of hydrogen fuel cells? a. engines that use hydrogen fuel are more efficient than gasoline-powered engines. b. the only emission produced by hydrogen fuel cells is water. c. hydrogen fuel is continually available and useful for heating. d. hydrogen fuel is often purified in a process that emits lots of greenhouse gases.

Which control would most likely achieve the greatest reduction of noise pollution? limiting airplane traffic insulating buildings and homes reducing road and highway traffic using headphones to listen to music building noise barriers beside highways

Which of these was not a direct result of the invention and subsequent use of eli whitney's cotton gin in 1793?