For which academic reasons have you used the internet? check all that apply. a. to research topics b. to access reference materials, such as encyclopedias c. to find the definition of words d. to search for maps or other geographic tools e. to read magazines, newspapers, and/or journal articles f. to access practice tests, quizzes, and flash cards

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.