a. transverse wave
b. longitutal wave
the strength of the gravitational force between two objects depends on the distance between their centers.
at higher altitude, the center of the earth is farther from the center of you, so the strength of the gravitational force between those two objects is less.
it's worth noting that frequency does not always increase when wavelength decreases. if you pass light through glass, its speed decreases and its frequency remains constant. this means the wavelength must decrease while the frequency stays the same. with waves it tends to be frequency that is constant.
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