HI who bored and need a companion;)

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

If we compare and contrast electromagnetic waves with sound waves, all but one statement is true. that is a) sound waves require a medium to travel while electromagnetic waves do not. b) electromagnetic waves can travel through the vacuum of space while sound waves cannot. c) electromagnetic waves must have a medium in which to travel, but sound waves can travel anywhere. eliminate d) sound waves must bounce off of matter in order to travel while electromagnetic waves do not require matter to be present.