Yes number two is the best IMHO. The large aperture selected has essentially isolated the frog as the main focus point.
BTW I like all the pictures....but WRT composition the other pics also isolate other, less interesting, features ( eg rocks, sticks, etc...). I have started to learn this in my work....some of my best pics seem to fill the frame with a single point of interest.
Of course I have seen many great pics that have several points of interest that "lead" your eye in a pleasing manner. For your pics I would almost consider this a portraiture...therefore a large aperture often works the best.
Thanks for sharing...