There is a misconception out there that anyone who owns a camera can be a professional photographer, but many untrained photographers don't know the rules of composition or posing before they set up shop.
A good photographer knows how to make their clients look their best. Part of this is achieved through posing.
1) In the image in the top right, the pose is less than flattering to the model because her torso isn't turned to the camera and her arms are placed flat against her sides. Also she needs to pull in her tummy and pull her shoulders back.
2) The top center image is a bit better but her upper arms are still flat against her sides.
3) In the top right, our model looks more naturally posed, and her weight is shifted to one hip, with her knee bent slightly on the other leg.
4) Bottom Left: This pose works because her hands are on her hips, which creates the illusion of a smaller waist.
5) Bottom Right: Not bad but her upper torso should be turned toward the camera.