How to find F0, F1, F2,

In the LPC spectrum in C you are looking for the first 3 peaks, which look to be about at 750, 1800 and 3000. The corresponding DFT spectrum in D gives you those same peaks (though the computed frequency will be somewhat different), but the problem is that you have to apply some complicated notions about bandwidth to figuring out which peak is the real peak (each harmonic is itself a peak, you only want the peak of peaks, those peaks that are stand out from other peaks). It is useful to know that the the fundamental is often "extra-prominent", which may keep you from identifying the 1st and 3rd harmonics in D as F1 and F2. A and B are more challenging in that you get 4 peaklets in A below 3000, but not 4 formants. You have to decide which ones to ignore: I am guessing that this is a vowel like [u]. Guessing formants from spectra a made easier if you have an expectation, which would tell you that 300, 800, 2700 is not appropriate for [a], which could lead you to pick different local maxima. This kind of peak-reading of spectra is pretty inaccurate in its relationship to the transfer function, which is what people are really interested in.