Definitely not the longest one as the length would just emphasise your short legs and make them look worse. For a pear shape I'd recommend a skirt, on the dress, that flows outwards and isn't too tight. This will balance out your natural curves and make your shape look great :) x
I would say the first one, because it is very flattering on the hips. The 2nd one is ok, the 3rd one only looks good on extremely long legs and last one isn't really flattering on anyone :)
Anything that is tighter on top and looser around my hips/butt is always a plus. Maxis that are more loose that I can belt is always a great match too.