Answer
See the answer below.
Work Step by Step
a) With $2000 cm^{-1}$ the wavelength is:
$5\times10^{-4}\ cm=5\ \mu m$
b) Since $E\propto 1/\lambda$, the left side is the high energy and the right side is the low energy.
c) O-H bonds since they have a bigger wavenumber
