How do scientists measure changes in the levels of global atmospheric co2? a. they have directly measured co2 in the atmosphere since 1758. b. they measure co2 levels in water trapped deep in earth's crust. c. they take ice core samples that allow measurement of co2 over hundreds of thousands of years. d. a and b. e. a, b, and c?

Two people each hold the end of a rope and create waves by moving their arms up and down. this wave is best classified as a transverse wave because a) both the rope particles and the wave are moving in the same direction. b) the wave is moving up and down as the particles of the rope move horizontally. c) the wave is moving horizontally as the particles of the rope move up and down. eliminate d) the wave is moving in a parallel direction with the motion of the person's arms.