Who wanna zoom (only people ages 8 and 13 are allowed sorry)

The medium that carries message signals from senders to receivers of communication is

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 of the following would most likely be a preservationist, as opposed to a conservationist, approach to public land management? i. allowing unrestricted boat access to a lake ii. allowing atv use in all areas of public land iii. closing fragile sections of a park to tourists i only ii only iii only i and iii ii and iii