If you're using a CRT monitor, you MUST calibrate and profile it regularly, at least once a month. As it's likely to be quite old now, once a week is probably more like it. I do extremely colour-critical work; when I used CRTs I calibrated and profiled daily.

A hardware profiling solution (e.g. the Spyder mentioned above) is a must. Make sure to let the monitor run for at least 20 minutes to warm up and stabilise. Your target settings should be 2.2 gamma, D65, 120 to 160 cd/Msq; ignore whatever the software recommends, rubbish that gets posted by half-wits in forums or stuff that you once read in a 10 year old book.

These days I use LCD NEC Reference monitors which I calibrate and profile weekly. Your sample images are tagged with an sRGB profile so I'm getting an accurate idea of what the images look like. The only ones I can provide meaningful comments on are B and C: C looks right, B doesn't.

---

Windows 10 x64 Pro - Intel Xeon E5450 @ 3.00GHz (x2)

PoserPro 11 - Units: Metres

Adobe CC 2017